Types of Asexual Reproduction:
1. Fission:
It is the type of reproduction in which body of a mature individual organism splits into two or more than two similar and equal sized daughters. In unicellular organisms, protists and monerans reproduction is by fission. Fission in further of three types viz Binary fission ,Multiple fission and plasmotomy.
Binary Fission:
It is the division of body of an individual in to two equal halves, each of which functions as an independent daughter individual. In unicellular organisms, binary fission is accompanied by mitotic division of nucleus followed by the cytokinesis. In metazoans the multicellular body is divided into two daughter individuals by a sort of cleavage. Binary fission in commonly present in protozoans by also occurs in certain animals like planarians.
Depending upon the plane of division Binary fission is further divided into three main types viz Irregular Binary Fission, Longitudinal Binary Fission and Transverse Binary Fission.
Irregular Binary Fission occurs in the Amoeba. Plane of division of the cytoplasm is variable but is always at right angles to the elongated dividing nucleus.
Longitudinal Binary Fission occurs in the flagellates like such like Euglena and Vorticella. The cytoplasm divides lengthwise forming two daughter cells.
Transverse Binary Fission occurs in the ciliates such as Paramecium. It also occurs in the planarians .Cytoplasm divides transversely between two sets of nuclei, forming two dissimilar daughter individuals.
It should be noted that in Binary fission, the parent body as a whole constitutes the reproductive unit, and disappears when its division is complete. However the parent can not said to have died as no dead body is left. Thus the organisms which undergo binary fission are said to be immortal.
Multiple Fission: Multiple fission is the division of parent body into many small daughter individuals simultaneously. Mutiple fission occurs in the protozoans like Plasmodium and Amoeba. In multiple fission, Nucleus of the parent cell divides a few to many times without division in the cytoplasm. Later the cytoplasm also divides, each part enclosing a nucleus. This process produces many daughter individuals from one parent at the same time.
Multiple Fission in Plasmodium and Amoeba.
In Plasmodium: In Plasmodium multiple fission takes
place in the active Schizont stage as well as in Sporont stage.The process if occurred in Schizont styage can be called as Schizogony and if it occurs in Sporont stage, it is termed as Sporogony. Dughter cells in the Sporogony are called as Sporozoites and in Schizogony are called as Merozoites.
In Amoeba: In Amoeba products of multiple fission become
individually surrounded by resistant coats the cyst walls, before their release from the parent. The multiple fission is here called as sporulation, and encysted products are called as spores. The spores remain inactive during the unfavorable conditions such as desiccation and extreme temperatures. On return of the favorable conditions, each cyst hatches into a small Amoeba, which gradually grows into an adult.
In multiple fission also the whole body acts as the reproductive unit and may disappear after the multiplication.
Plasmotomy: Plasmotomy is the division of multinucleate protozoans into several small, multinucleate daughters without nuclear divisions. Daughters grow and regain normal number of nuclei by nuclear divisions.It occurs in the Opalina and Pelomyxa.
2)Budding :
It is the type of reproduction in which individuals are developed from the outgrowths or small projections called as buds. It occurs in some protozoans and certain lower invertebrates such as sponges, coelenterates, annelids and tunicates.
During this process the parent body may form a single or many buds. A
bud gradually assumes the form and size of the parent. In protozoans, the bud separates from the parent body and grows into an adult while leading an independent life.
Buds may be external as well as Internal with regard to the position of buds.
External Buds arise from the surface of the parent body such as Hydra and Scypha.
Internal Buds are formed within the parent’s body in fresh water sponges such as Spongilla. These consist of small groups of cells called as archaeocytes, enclosed by resistant protective coat strengthened by spicules.They are called as gemmules .A gemmule germinates into a new sponge under favourable conditions.
3)Fragmentation: It is the type of reproduction in which the animal’s
body is broken up into pieces, each of which develops into a new individuals. It occurs in the flatworm Microstomum. Large sponge and coelenterate colonies may break up into fragments by wave action, animal activity, and death and decay of old parts. Each fragments develop into a new colony in due course of time. Fragmentation is always accompanied by regeneration.
Significance of Asexual Reproduction:
Asexual reproduction brings about multiplication of the species only. It does not play a role in evolution or no variation is introduced into new individuals formed by it. Asexual reproduction is theoretically most advantageous in stable, favourable environment because it perpetuates successful genotypes precisely.
Sex determination :-:Establishment of sex through differential development in an individualan at early stage of life is called as sex determination.
(Additional Information)History of Sex Determination ::-
How an individual's sex is determined has been one of the most studied question in the history of embryology. Aristotle who collected and dissected embryos claimed that sex was determined by heat of male partner during sexual intercourse. Thus more heated the passion, Greater the probability of offspring to be male. Aristotle told that women were fundamentally men whose development was arrested too early. The female was mutilated male whose development had stopped because the coldness of mother's womb overcame the heat of the Father's semen. Women were therefore considered more colder and passive than men and female sexual organs had not developed to the point at which they could provide active seeds. This view was accepted by Christian Church and by a renowned author of anatomical textbooks namely Gelan.
The view of Aristotle remained famous over a thousand years. As late as 1543, Andreas vesalius held the view. By the end of 1500 anatomist had rejected Gelan's representation of female anatomy. During 1600s and 1700s females were found to be producing eggs that could transmit parental traits, therefore physiology of sex organs began to be studied.Until late 20th century environment was believed to be important in determining sex. In 1905, correlation of female sex with XX sex chromosome and of me sex with XY sex chromosomes was established. This finding suggested strongly that specific nuclear component was necessary for detecting the development sexual phenotype.
Methods of sex determination( compulsory part) :-
There are both environmental as well as internal mechanisms of sex determination those can be operated in different species.
Four main modes of sex determination are as:
1) Environmental Sex determination
2) Allosomic sex determination
3) Non-allosomic sex determination
4) Haplodiploidy
Environmental Sex determination:- It is a non genetic mode of sex determination in which environmental conditions determine the sex of the offspring. Organisms are capable to develop into any of the two possible sexes. Eg. In marine worm Bonellia,larva develops into female if it settles down alone in an isolated place . Any larva coming in contact with already developed female remains small and develops into a male. It enters the body of female and lives in its uterus as a parasite.
In crocodiles low temperature is responsible to induce female characters into a larva while as high temperature induces maleness. In turtles temperature below 28° C induces maleness and above33°C induces female Ness in larvae. If temperature is between 28°C and 33°C equal umber of male and female offspring are developed.
Non- Allosomic Genetic Sex determination:- In this type of sex determination, fertility factor is present in the non- Allosomes. In Chlamydomonas the genes controlling male and female characters more technically (+) and ( -) characters are regulated by the genes those are present in the Autosomes. In maize sex chromosomes are absent. There are two separate genes. One determines the development of male inflorescence while other is responsible for development of female inflorescence on the cob.
Allosomic Genetic Sex Determination:- in this type sex is determined by specific chromosomes called as Sex chromosomes or Allosomes. Sex chromosome in the form of X body was first seen in fire fly by Henking in 1891. In 1902 Stevens discovered Y chromosome. Late in 1905 Steven and Wilson gave chromosomal theory of sex determination with two types of sex chromosomes X and Y.
Types of Allosomic sex determination are as under:
(Important question)1) XX-XY type of sex determination ( Sex determination in human beings):-
The female in this type of sex determination female is homomorphisms with two similar sex chromosomes,XX. Male is heteromorphic containing two types of sex chromosomes XY. Y chromosome is shorter in length than X chromosome and is morphologically different. Despite difference in morphology X and Y chromosomes synapse during cell cycle. The synapsing part is called as homologous region and the region which does not synapse is called as differential region. Genes present in homologous region are similar and are called XY linked genes. Sex if the baby is determined by type of sperm that fuses with the egg. Female is homogametic and produces only one type of eggs with XY chromosomes. Male is heterogametic and produces two types of sperms 50% of sperms contain X chromosomes and 50% of the sperms contain Y chromosomes. If sperm contains Y chromosome along with 22 Autosomes, such sperm is called as androsperm(22+Y). On the other hand when sperm contains X chromosome with 22 Autosomes such sperm is called as gynosperm(22+X).
If androsperm fuses with the egg sex of the offspring will be male. On the other hand if gynosperm fuses with the egg,sex of the offspring is female. Such a method of sex determination is called as male heterogamety.
2) XX -XO type of sex determination :- This mode of sex determination is found in round worms,grasshoppers, cockroaches,true bugs and some plants viz Vellisneria and Discorea Females contain two similar sex chromosomes XX. Therefore they are homogametic producing single type of gametes Autosomes A + sex chromosome X i.e (A+X). Males possess only one sex chromosome. X chromosome present in male is similar to that present in females. Males are heterogametic forming two types of gametes viz (A+X) gynosperm and (A+O) androsperm. Fusion of androsperm (A+O) with an egg forms male offspring while as fusion of gynosperm (A+X) with an egg forms female offspring.
(Important question)3) ZW-ZZ sex determination or sex determination in birds:- This method of sex determination occurs in birds,some reptiles, fished and some plants. Both sexes male as well as female have two sex chromosomes. However the female hasheteromorphic sex chromosomes (ZW) while males have homomorphic sex chromosomes (ZZ). Females produce two types of eggs , male forming (A+Z) and female forming (A+W). Male produces similar type of gametes with (A+Z) chromosomes. Unlike human beings where male sex determine the sex of child,in birds sex of the offspring is dependent upon female gamete. Such type of sex determination is called as female heterogamety.
4) ZO-ZZ sex determination (Sex determination in butterflies and moths):- females of butterflies and moths possess a single sex chromosome (AA+ZO) while as males have two sex chromosomes (AA+ZZ). Males are homogametic producing single type of gametes (A+Z). On the other hand females produce two types of gametes male producing (A+Z) and female producing (A+O).
5) Haplodiploidy(Sex determination in honey bees):-(important question) In this type of sex determination one sex is Haploid while as other is diploid .
Female is diploid which is formed by fusion of two Haploid gamete cells. On the other hand male is Haploid which is formed directly from unfirtilized eggs. As the egg directly gives rise to male offspring so the process is called as arrhenotoky , arrhenotokous parthenogenesis or Haploid parthenogenesis.
In honey bees, female is diploid while as the males are Haploid. Males develop through arrhenotokous parthenogenesis or Haploid parthenogenesis. Male honey bees or drones produce sperms through mitosis. They are stored by female after receiving during the nuptial flight. The female produces Eggs through meiosis. They are fertilized by the stored sperms to produce female offspring. When required one cell is enlarged and the female offspring is fed on royal jelly to convert them into queen. All other females are fed over by been bread. They are changed into sterile workers. While all workers and Queen have both mother and father, drones or males have neither father nor they have sons, they only have grandfather's and grandsons.
Reproductive health:
Reproductive health is a state of physical, emotional,
behavioral and social fitness for leading a responsible, safe
and satisfying reproductive life. Briefly speaking,reproductive life refers to the healthy reproductive organs
with normal functioning. WHO has defined reproductive
health as total wellbeing in all aspects of reproduction i.e. its
emotional, social and behavioral one. A society will be
reproductively healthy if its members possess not only
physically and functionally normal reproductive organs but
also have normal emotional and behavioral interactions
among them in all sex related aspects.
Significance of reproductive health:
1)Awareness is provided to both males and females to
lead healthy and satisfactory reproductive life.
2)Making mature individuals of the society aware of
fertility regulating methods.
3)Providing information so as to keep proper hygiene of
genitalia.
4)Protection is made possible against the STDs.
5)Planning children to the limit of enjoying family life.
6)Obtaining treatment for reproductive diseases at the
early stage.
Problems and strategies
Involved in reproductive health
Problems:
i) Taboos:- usually in several country including India,
religions, traditions, and social set up do not allow much
sharing of knowledge about reproductive health to the
children.
ii) Early marriage:- children were often married in early
stages when they were kids.
iii) Kid parents:- early marriages often lead to the
condition in which kids become parents. They are not
well prepared physically as well as mentally to coup up
with such conditions.
iv) Career:-After marriage it becomes impossible to
children to pursue higher degrees and a prosperous
career. So the career of the married kids may be spoiled.
v) Teenage lady:-The married teenagers are not
physically and mentally fit to have children. It often
leads to the life threatening conditions.
vi) Deformities:- children of early marriage often have the
risk of malformations and deformities.
vii) Neonatal and Maternal Death rates:-Maternal
mortality rate as well as neonatal mortality rate is
usually high in case of child marriages.
viii) Personal hygiene :- Carelessness of maintaining
personal hygiene and hygiene of reproductive organs
results in catching up STDs.
ix) Health of ladies:- Due to early marriage and becoming
parent in early life causes weakness of lady. She
becomes anaemic and prone to infections.
x) Population growth:- after all above discussed problems
caused due to the early marriage there is a serious
threat of population explosion as the population growth
is increasing day by day.
Strategies:- In 1951 India initiated family planning and
hence became the first country to initiate the planning and
programs to improve reproductive health. Program became
successful so India started another program under the name
Reproductive and Child Health Care (ICH) in 1997, which
was more comprehensive than the previous one. It was
based on three main goals viz Reproductive health, child
care and fertility regulation. All these goals may be fulfilled
by adapting few strategies as discussed below:
1)General awareness:-Various organizations including
Govt. and Non Govt. organizations are involved in
providing awareness to the people regarding
different aspects of reproductive health, through
print media, electronic media, social media, seminar
and other programs.
2)Elders:- elders including teachers, parents, and
religious heads are responsible to provide knowledge
and awareness about sex related aspects andparticularly sex related problems and drawbacks of
early sexual relationships.
3)Sex education:-it has been and should be added to
the curriculum at high school and college levels so as
to provide sound knowledge about reproductive
health to the younger generation. It will help in
reducing myths, miss beliefs and threats regarding
various sex related problems, and will provide
knowledge to make children know the consequences
of indulgence in early sexual relationships.
4)Family welfare information:- All persons at the
marriageable age should have information regarding
birth control options, reasons of failure to conceive(
to have children), Care of would-be-mother, post
natal care of mother and child, importance of breast
feeding etc.
5)Uncontrolled population :- It is necessary to aware
the married couples about consequences of
overpopulation.
6)Social evils and crimes:- information should be
spread about sex abuses and crimes.
7) Infrastructure:-Proper infrastructure should be
provided besides the expertise and material support
for attaining reproductive health through providing
assistance in sex related problems like pregnancy,
delivery, contraception, infertility and STDs.8) Sex determination:- It is a strategy by which sex of
the child can be checked before birth through
amniocentesis or Sonography. Nowadays there is ban
on both the processes.
9) Marriageable Age:- Marriageable age has been fixed
as 21 years for boys and 18 years for girls.
10) Research:- Researches are still going on to design
new techniques and methods of contraception. For
instance Central drug research institute (CDRI)
luknow has developed “saheli” a new steroid,
contraceptive one week pill.
1. Fission:
It is the type of reproduction in which body of a mature individual organism splits into two or more than two similar and equal sized daughters. In unicellular organisms, protists and monerans reproduction is by fission. Fission in further of three types viz Binary fission ,Multiple fission and plasmotomy.
Binary Fission:
It is the division of body of an individual in to two equal halves, each of which functions as an independent daughter individual. In unicellular organisms, binary fission is accompanied by mitotic division of nucleus followed by the cytokinesis. In metazoans the multicellular body is divided into two daughter individuals by a sort of cleavage. Binary fission in commonly present in protozoans by also occurs in certain animals like planarians.
Depending upon the plane of division Binary fission is further divided into three main types viz Irregular Binary Fission, Longitudinal Binary Fission and Transverse Binary Fission.
Irregular Binary Fission occurs in the Amoeba. Plane of division of the cytoplasm is variable but is always at right angles to the elongated dividing nucleus.
Longitudinal Binary Fission occurs in the flagellates like such like Euglena and Vorticella. The cytoplasm divides lengthwise forming two daughter cells.
Transverse Binary Fission occurs in the ciliates such as Paramecium. It also occurs in the planarians .Cytoplasm divides transversely between two sets of nuclei, forming two dissimilar daughter individuals.
It should be noted that in Binary fission, the parent body as a whole constitutes the reproductive unit, and disappears when its division is complete. However the parent can not said to have died as no dead body is left. Thus the organisms which undergo binary fission are said to be immortal.
Multiple Fission: Multiple fission is the division of parent body into many small daughter individuals simultaneously. Mutiple fission occurs in the protozoans like Plasmodium and Amoeba. In multiple fission, Nucleus of the parent cell divides a few to many times without division in the cytoplasm. Later the cytoplasm also divides, each part enclosing a nucleus. This process produces many daughter individuals from one parent at the same time.
Multiple Fission in Plasmodium and Amoeba.
In Plasmodium: In Plasmodium multiple fission takes
place in the active Schizont stage as well as in Sporont stage.The process if occurred in Schizont styage can be called as Schizogony and if it occurs in Sporont stage, it is termed as Sporogony. Dughter cells in the Sporogony are called as Sporozoites and in Schizogony are called as Merozoites.
In Amoeba: In Amoeba products of multiple fission become
individually surrounded by resistant coats the cyst walls, before their release from the parent. The multiple fission is here called as sporulation, and encysted products are called as spores. The spores remain inactive during the unfavorable conditions such as desiccation and extreme temperatures. On return of the favorable conditions, each cyst hatches into a small Amoeba, which gradually grows into an adult.
In multiple fission also the whole body acts as the reproductive unit and may disappear after the multiplication.
Plasmotomy: Plasmotomy is the division of multinucleate protozoans into several small, multinucleate daughters without nuclear divisions. Daughters grow and regain normal number of nuclei by nuclear divisions.It occurs in the Opalina and Pelomyxa.
2)Budding :
It is the type of reproduction in which individuals are developed from the outgrowths or small projections called as buds. It occurs in some protozoans and certain lower invertebrates such as sponges, coelenterates, annelids and tunicates.
During this process the parent body may form a single or many buds. A
bud gradually assumes the form and size of the parent. In protozoans, the bud separates from the parent body and grows into an adult while leading an independent life.
Buds may be external as well as Internal with regard to the position of buds.
External Buds arise from the surface of the parent body such as Hydra and Scypha.
Internal Buds are formed within the parent’s body in fresh water sponges such as Spongilla. These consist of small groups of cells called as archaeocytes, enclosed by resistant protective coat strengthened by spicules.They are called as gemmules .A gemmule germinates into a new sponge under favourable conditions.
3)Fragmentation: It is the type of reproduction in which the animal’s
body is broken up into pieces, each of which develops into a new individuals. It occurs in the flatworm Microstomum. Large sponge and coelenterate colonies may break up into fragments by wave action, animal activity, and death and decay of old parts. Each fragments develop into a new colony in due course of time. Fragmentation is always accompanied by regeneration.
Significance of Asexual Reproduction:
Asexual reproduction brings about multiplication of the species only. It does not play a role in evolution or no variation is introduced into new individuals formed by it. Asexual reproduction is theoretically most advantageous in stable, favourable environment because it perpetuates successful genotypes precisely.
Reproduction:
It is the ability of living organisms to produce a new generation of living individuals similar to themselves. It is one of the fundamental characteristics of living organisms. Reproduction is aimed at increasing population and perpetuation of species. In other words it provides the group immortality by replacing the dead individuals with new born ones.
Functions of reproduction:
1) Continuity of race: A species continues to live indefinitely only because of reproduction of its individuals.
2) Replacement: It replaces the dead individuals by the new ones.
3) Population Organization: Reproduction helps to maintain the population organization consisting of young ones, adults and aged ones.
4) Life: Life can only exist on earth if there is reproduction of living organisms.
5) Variations: Reproduction introduces variations in structure, function and behavior. They produce individuality of living beings.
6) Useful variations: Useful variations occur in living organisms and they are passed on to the next generations.
Basic features of Reproduction:
1) Important common features of reproduction in all living organisms include DNA replication.
2) Formation of RNAs, proteins and other biomolecules for multiplication of cellular contents.
3) Growth of cells.
4) Division of cells. It is mode of reproduction in many unicellular organisms.
5) Formation and separation of reproductive units.
6) Development of new individuals from reproductive units.
Asexual Reproduction:
It is the type of reproduction in which the individuals are developed from single parents without formation and fusion of gametes. Meiosis has no role in the asexual reproduction and hence it involves only mitotic divisions. Offspring formed during asexual reproduction are the identical copies of their parents. They are clones of their parents as well as of one another. The term ramets is used for the members of the clone. Asexual reproduction is common in the unicellular organisms and simple plants and animals.
Characteristics of asexual reproduction:
i) It is uniparental which means individuals get all the traits and all the genetic materials from the single parent.
ii) Reproductive unit is the specialized and unspecialized part of the parent.
iii) Propagule or reproductive units is generally formed from the somatic cells of the parent. Therefore asexual reproduction is also called as somatogenic reproduction.
iv) There is no fusion of gametes because of which asexual reproduction is also called as agamogamy or agamogenesis.
v) All the divisions are mitotic therefore Meiosis is absent.
vi) Young ones are the exact copies of their parents and also of one another.
vii) There are no haploid-diploid alternations.
viii) Asexual reproduction is a quick method of multiplication.
Human Reproductive systems: Reproductive systems are a set of interdependent and inter connected organs and body components which take part in sexual reproduction. Human males and femaleshave different reproductive systems. Which are made up of two types of sex organs viz primary and secondary.
Primary Sex Organs are the organs that produce gametes. They are also called as gonads. Gonads possess germinal cells which divide and mature into gametes. Gonads of male are called as called as testes and that of the females are called as ovaries. Functioning of the gonads is under the control of FSH and LH hormones from the anterior lobe of pituitary gland.
Secondary Sex Organs are the organs, glands and which do not produce gametes and hormones but are otherwise essential for the sexual reproduction. Secondary sex organs of male reproductive system are vasa efferentia, epididymis, vasa deferentia, ejaculatory ducts, seminal vesicles, Cowper’s glands, urethra, prostate gland and penis.
Secondary organs of female reproductive systems include fallopian tubes, uterus, vagina, external genitalia, Bartholin’s glands and mammary glands.
Male Reproductive System:
It is the system of sex organs and accessory glands found in the human male which is specialized in formation, storage, nourishment and conduction of sperms.It is located in the pelvic region.It consists of a pair of testes, number of accessory ducts, accessory glands and external genitalia.Accessory glands are rete testis, Vasa efferentia, epididymis, vasa deferentia, ejaculatory ducts and urinogenital duct.Seminal vesicles, Prostate gland and Cowper’s glands are accessory glands. Scrotum and Penis are the external genitalia.
i) Testes:
Testes are the primary sex organs or compound tubular glands .They are smooth , soft , pinkish and oval organs about 4-5 cm long, 2.5cm wide and 3 cm thick .Testes are about 12g in weight. They are extra-abdominal and are suspended in scrotal sacs by spermatic cords. Testes are covered by three protective coverings called as tunicae.
Tunicae: Testes are covered in a dense fibrous coat, the tunica albuginea which is actual covering of the testes. The covering is made of dense bluish white fibrous or collagenous connective tissue. Tunica albuginea also passes into the testes to form incomplete vertical columns called as mediastinum and a number of septa. Lining the tunica albuginea on the outer side there is a thin layer or coat of Tunica Vasculosa which is formed of lose connective tissue. It is the delicate layer which lines the testicular lobules inner to the tunica albuginea. This layer has rich supply of blood capillaries.
Outer most layer of the testes around the most of the testes is a visceral layer of peritoneum called as Tunica Vaginalis. Tunica Vaginlais is like a flat sac filled having a narrow coelomic cavity filled with the coelomic fluid. Its membranous covering is made up of peritoneum .This protective layer helps the testes in frictionless sliding.
Testicular Lobules: Tunica albuginea divides the major part of testes into about 200 to 300 testicular lobules by forming transverse septa and a vertical mediastinum. Each lobe is filled with connective tissue and 1-3 seminiferous tubules. Total number of seminiferous tubules in testes are about 500.They are highly coiled with each seminiferous tubule being 70-80 cm in length. The ends of the seminiferous tubules converge to form straight towards middle of the posterior surface of the testes to form straight tubules called as tubuli recti. Tubuli recti open into a network of wider, irregular tubules called as rete testes. Here some of the epithelial cells contain a single cilium to aid the sperm transport.
Each seminiferous tubule is lined by germinal epithelium. Majority of the cells in epithelium are cuboidal spermatogenic cells but some are large, pyramidal, supporting cells called as sertoli cells or nurse cells.Sertoli cells were discovered by the Italian histologist, Enricho Sertoli. Cuboidal cells produce spermatogonia by mitosis into the lumen of the seminiferous tubules. The spermatogonia grow into primary spermatocytes, which undergo meiosis to producing haploid secondary spermatocytes and then spermatids. The latter metamorphose into the spermatozoa.
Small group of large, polygonal cells termed as Leydig’s cells or Interstitial Cells lie in the connective tissue present between seminiferous tubules.These cells secrete male sex hormone Testosterone in blood.
ii) Vasa Efferentia: They are 10-20 fine tubules which connect rete testes with the epididymis. The epithelium has large ciliated cells and small cells with endocytic activity. Cilia aid in the sperm movements while as endocytic cells help in removing the cell debris accompanying sperms. Tubuli recti, rete testes, and vasa efferentia together form the intratesticular genital duct system.
iii) Epididymis: They are a pair of ducts from each testes formed by the union of its vasa efferentia. It is a long, narrow, highly coiled compacted tubule which lies on upper, lower and back sides of the testes. It is about 6 m in length. Coiling of the epididymis forms three regions viz upper caput epididymis or head, middle corpus epididymis or body and lower cauda epididymis or tail. Spermatozoa undergo morphological changes in the head ofthe epididymis acquiring the higher motility and fertilization capacity. Then the sperms are temporarily stored in the tail of the epididymis before entering the vasa deferentia. Epididymis shows peristalsis and segmenting contractions to push the sperms forward.
iv) Vasa Deferentia: Vas deference is the continuation of cauda epididymis. It is about 40 cm long and is slightly coiled at first but becomes straight as it enters the abdominal cavity through inguinal canal. Here it passes over urinary bladder, curves round the ureter and joins the duct of seminal vesicle to form an ejaculatory duct. Near its end vasa deferentia is enlarged to form a spindle- like ampulla for the temporary storage of spermatozoa.
v) Ejaculatory ducts: These are about 2 cm long thin walled tubes that pass through the prostate gland and open into the urethra.
vi) Urethra: It is the urinary duct leading from urinary bladder. From the point it is joined by ejaculatory ducts, it carries urine as well as sperms and seminal fluids. It also receives the secretions of prostate and Cowper’s glands. Urethra is some 20 cm long and passes through the penis. It has three main regions viz, prostatic urethra, membranous urethra and penile urethra.
It has two sphincters one is called as internal sphincter and other is termed as external sphincter.
vii) Penis: It is an external intromittent organ through which the urethra passes. It contains three columns of spongy tissue viz two columns of corpora cavernosa and one corpus spongiosum. Near the tip of the penis corpusspongiosum is enlarged to form a highly sensitive Glans penis.
viii) Scrotum: It is the pouch of pigmented skin arising from lower abdominal wall. Its dermis contains almost a continuous layer of smooth muscle fibres called as dartus tunic. Scrotum is divided internally into two chambers by a partition called as septum scroti.
ix) Accessory glands: These include a pair of seminal vesicles, prostate gland, and a pair of Cowper’s glands or bulbourethral glands.
a. Seminal Vesicles: these are elongated, coiled sacs about 4 cm long, located near the ampulla of the vas deference. Seminal vesicle contribute a yellowish, slightly alkaline viscous seminal fluid that contains the sugar fructose, a coagulating enzyme, ascorbic acid and prostaglandins.
b. Prostate gland: The prostate gland surrounds the first portion of the urethra. It is large, chestnut shaped, lobulated and spongy gland. It secretes thin, milky, slightly acidic fluid, which is discharged into prostatic part of urethra. It contains citrate, and anticoagulant enzymes.
c. Cowper’s glands: Cowper’s gland also called as bulbourethral gland lie below the prostate gland. They are about the size of pea seeds and secrete alkaline mucus which is discharged into membranous part of urethra. The mucus coats urethra before the sperms are released.
Female Reproductive system
Female reproductive system consists of a pair of ovaries, oviducts, uterus, vagina, external genitalia and mammary glands.
1) Ovaries: ovaries are a pair of primary sex organs of female. These are about a size and shape of almond. They are about 3 cm long, 2 cm wide and 1 cm thick. Ovaries lie in the lower abdomen held to the broad ligament by double folds of peritoneum, the mesovaria. Each ovary is connected to the uterus by ovarian ligament and to the lateral pelvic wall by suspensory ligaments.
Ovaries are solid organs and are composed of connective tissue, The stroma, wrapped by a layer of cuboidal cells, the germinal epithelium, followed by a layer of flattened cells, the visceral peritoneum. The stroma consists of outer cortex and central medulla. The ovarianmedulla contains various rounded bodies called as ovarian follicles. Each follicle contains an ovum surrounded by various layers of follicular cells. The follicle cells of a mature follicle secrete estrogen into the blood. Once in a month, most mature ovum from one ovary is released. The ovarian cortex contains young and mature follicles. There are millions of primary follicles present in the ovary out of which only 60,000-80,000 follicles remain in the ovary at the time of puberty. For becoming a mature (Graafian) follicle a primary follicle undergoes various changes to pass secondary follicle, and tertiary follicle stages.
Ovarian follicles: They are oocyte containing complexes which occur in denser part of cortex. The number of primary follicles in each ovary of a young adult female is about 60,000-80,000. Among this large number of primary follicles only 450 follicle become mature during the whole reproductive span. While others degenerate. The degeneration of follicles is also called as follicular atresia.
Ovarian follicle contains a secondary oocyte covered by granulosa cells and theca cell layers. Granulosa cells are derived from germinal epithelium while as theca develops from the cells of cortex. Theca gets differentiated into outer theca externa andinternal theca interna. Granulosa cells secrete a fluid called as liquor folliculi which creates a large cavity called as antrum. It shifts the oocyte to one side. A stalk or pedicel develops between oocyte and granulosa layer. This stalk is called as cumulus oophorus. Cells surrounding the oocyte elongate radially and form a layer called as corona radiata. Oocyte which is covered by a plasma membrane called as oolemma. Outer to oolemma there is a non-cellular glycoprotein layer called as Zona pellucida. Both zona pellucida and oolemma contain receptor proteins.
During ovulation a ovum gets detached from Graafian follicle and leaves the ovary which is later on taken up by the infundibulum of oviducts.
2) Fallopian tubes or Oviducts: They are a pair of muscular tubes of about 10-12 cm length which lie horizontally in peritoneal cavity above and behind the urinary bladder. Oviduct had four main parts viz Infundibulum, Ampulla, Isthmus, and uterine part.
Infundibulum: It is a funnel shaped fimbriated free end of the oviduct. There is a central pore called as ostium. Margin of fimbriated part of oviduct contains finger like processes called as fimbriae for catching released ovum.
Ampulla: It is curved, dilated part of the oviduct. The lumen of which has a network of plicae.
Isthmus: It forms a straight part of oviduct which connects ampulla with the lateral part of uterus. Lumen of isthmus is narrow. Fertilization of ovum occurs at the junction between Isthmus and Ampulla.Uterine part: It is the part of oviduct which passes into uterus. It is about 1 cm long and controls passage of ovum through muscular movements.
3) Uterus: It is an inverted pair shaped large part of the female reproductive system also called as womb which is specialized for enchoring and nourishing the developing foetus. Uterus is supported in its position by ligaments that attach it to pelvis. It is anteflexed at right angles to the vagina above and behind the urinary bladder in the area of rectum. The size of empty uterus is about is 7.5 cm in length, 5 cm in breadth, and 2.5 cm in thickness.It enlarges to over 100 times during pregnancy in order to accommodate the foetus amniotic fluid surrounding it. Uterine wall is thick and muscular. It is differentiated in to three main layers viz endometrium, myometrium and perimetrium.
Endometrium has two parts, epithelium and lamina propria. Epithelium lines the luminal surface of the uterus. It contains two types of columnar cells, ciliated and secretory. Lamina propria contains connective tissue with fibroblasts, tubular glands, and blood vessels. Endometrium shows cyclic changes during menstrual cycle. It is later on regenerated. Myometrium undergoes strong muscular contractions during delivery of a baby. Perimetrium is outer most layer of the uterus.
Uterus is differentiated into three main regions viz fundus, body and cervix.
Fundus is the upper dome shaped part of the uterus which lies above the level of entry of oviducts. Body is the main part of uterus. It is broad towards the fundus and narrower towards the cervix. Theregion of entry of oviducts is called as cornua. Cervix is the small narrow, cylindrical inferior extremity of the uterus which is about 2.5 cm in length. Along with the vagina, cervical canal is also called as birth canal.
4)Vagina: It is an elastic tube about 8-10cm in length which functions as female copulatory organ, pathway for menstrual flow and birth canal it opens outside into the vestibule through an aperture called as vaginal orifice. Internally vagina contains two longitudinal ridges and a number of transverse rugae. In virgins vaginal orifice is partially covered by a thin membrane called hymen.
5)External genitalia: they are external structures associated with the passage of female genital tract. There is central depression called as vestibule. The sides contain folds called as labia. Some other parts associated are as:
a. Mons pubis: It is anterior rounded fleshy prominence present in the region of pubic symphisis. Skin of this area contains pubic hairs.
b. Perineum : It is an area between vestibule and anus.
c. Clitoris: It is an erectile finger like organ present below Mons pubis at the anterior tip of vestibule above urethral opening at the upper junction of two folds of labia minora. A small sensitive tubercle of erectile tissue occurs at the tip of clitoris which is called as glans clitoridis. It is covered by prepuce.
d. Vestibule : It is the depression present in the region of vulva which contains clitoris and two openings, vaginal orifice and urethral orifice.
e. Labia minora : They are a pair of narrow fleshy folds present around the vestibule devoid of hair but contain sebaceous glands.
f. Labia majora: They are a pair of large thicker fleshy folds which lie on sides of vestibule outside the labia minora from mons pubis to perineum.
6)Associated glands: Human female reproductive tract is not having so much glands. The vaginal glands are Bartholin’s gland or tubulo-alveolar glands located in the lateral walls of vestibule. They secrete a lubricative mucus at the time of copulation
Primary Sex Organs are the organs that produce gametes. They are also called as gonads. Gonads possess germinal cells which divide and mature into gametes. Gonads of male are called as called as testes and that of the females are called as ovaries. Functioning of the gonads is under the control of FSH and LH hormones from the anterior lobe of pituitary gland.
Secondary Sex Organs are the organs, glands and which do not produce gametes and hormones but are otherwise essential for the sexual reproduction. Secondary sex organs of male reproductive system are vasa efferentia, epididymis, vasa deferentia, ejaculatory ducts, seminal vesicles, Cowper’s glands, urethra, prostate gland and penis.
Secondary organs of female reproductive systems include fallopian tubes, uterus, vagina, external genitalia, Bartholin’s glands and mammary glands.
Male Reproductive System:
It is the system of sex organs and accessory glands found in the human male which is specialized in formation, storage, nourishment and conduction of sperms.It is located in the pelvic region.It consists of a pair of testes, number of accessory ducts, accessory glands and external genitalia.Accessory glands are rete testis, Vasa efferentia, epididymis, vasa deferentia, ejaculatory ducts and urinogenital duct.Seminal vesicles, Prostate gland and Cowper’s glands are accessory glands. Scrotum and Penis are the external genitalia.
i) Testes:
Testes are the primary sex organs or compound tubular glands .They are smooth , soft , pinkish and oval organs about 4-5 cm long, 2.5cm wide and 3 cm thick .Testes are about 12g in weight. They are extra-abdominal and are suspended in scrotal sacs by spermatic cords. Testes are covered by three protective coverings called as tunicae.
Tunicae: Testes are covered in a dense fibrous coat, the tunica albuginea which is actual covering of the testes. The covering is made of dense bluish white fibrous or collagenous connective tissue. Tunica albuginea also passes into the testes to form incomplete vertical columns called as mediastinum and a number of septa. Lining the tunica albuginea on the outer side there is a thin layer or coat of Tunica Vasculosa which is formed of lose connective tissue. It is the delicate layer which lines the testicular lobules inner to the tunica albuginea. This layer has rich supply of blood capillaries.
Outer most layer of the testes around the most of the testes is a visceral layer of peritoneum called as Tunica Vaginalis. Tunica Vaginlais is like a flat sac filled having a narrow coelomic cavity filled with the coelomic fluid. Its membranous covering is made up of peritoneum .This protective layer helps the testes in frictionless sliding.
Testicular Lobules: Tunica albuginea divides the major part of testes into about 200 to 300 testicular lobules by forming transverse septa and a vertical mediastinum. Each lobe is filled with connective tissue and 1-3 seminiferous tubules. Total number of seminiferous tubules in testes are about 500.They are highly coiled with each seminiferous tubule being 70-80 cm in length. The ends of the seminiferous tubules converge to form straight towards middle of the posterior surface of the testes to form straight tubules called as tubuli recti. Tubuli recti open into a network of wider, irregular tubules called as rete testes. Here some of the epithelial cells contain a single cilium to aid the sperm transport.
Each seminiferous tubule is lined by germinal epithelium. Majority of the cells in epithelium are cuboidal spermatogenic cells but some are large, pyramidal, supporting cells called as sertoli cells or nurse cells.Sertoli cells were discovered by the Italian histologist, Enricho Sertoli. Cuboidal cells produce spermatogonia by mitosis into the lumen of the seminiferous tubules. The spermatogonia grow into primary spermatocytes, which undergo meiosis to producing haploid secondary spermatocytes and then spermatids. The latter metamorphose into the spermatozoa.
Small group of large, polygonal cells termed as Leydig’s cells or Interstitial Cells lie in the connective tissue present between seminiferous tubules.These cells secrete male sex hormone Testosterone in blood.
ii) Vasa Efferentia: They are 10-20 fine tubules which connect rete testes with the epididymis. The epithelium has large ciliated cells and small cells with endocytic activity. Cilia aid in the sperm movements while as endocytic cells help in removing the cell debris accompanying sperms. Tubuli recti, rete testes, and vasa efferentia together form the intratesticular genital duct system.
iii) Epididymis: They are a pair of ducts from each testes formed by the union of its vasa efferentia. It is a long, narrow, highly coiled compacted tubule which lies on upper, lower and back sides of the testes. It is about 6 m in length. Coiling of the epididymis forms three regions viz upper caput epididymis or head, middle corpus epididymis or body and lower cauda epididymis or tail. Spermatozoa undergo morphological changes in the head ofthe epididymis acquiring the higher motility and fertilization capacity. Then the sperms are temporarily stored in the tail of the epididymis before entering the vasa deferentia. Epididymis shows peristalsis and segmenting contractions to push the sperms forward.
iv) Vasa Deferentia: Vas deference is the continuation of cauda epididymis. It is about 40 cm long and is slightly coiled at first but becomes straight as it enters the abdominal cavity through inguinal canal. Here it passes over urinary bladder, curves round the ureter and joins the duct of seminal vesicle to form an ejaculatory duct. Near its end vasa deferentia is enlarged to form a spindle- like ampulla for the temporary storage of spermatozoa.
v) Ejaculatory ducts: These are about 2 cm long thin walled tubes that pass through the prostate gland and open into the urethra.
vi) Urethra: It is the urinary duct leading from urinary bladder. From the point it is joined by ejaculatory ducts, it carries urine as well as sperms and seminal fluids. It also receives the secretions of prostate and Cowper’s glands. Urethra is some 20 cm long and passes through the penis. It has three main regions viz, prostatic urethra, membranous urethra and penile urethra.
It has two sphincters one is called as internal sphincter and other is termed as external sphincter.
vii) Penis: It is an external intromittent organ through which the urethra passes. It contains three columns of spongy tissue viz two columns of corpora cavernosa and one corpus spongiosum. Near the tip of the penis corpusspongiosum is enlarged to form a highly sensitive Glans penis.
viii) Scrotum: It is the pouch of pigmented skin arising from lower abdominal wall. Its dermis contains almost a continuous layer of smooth muscle fibres called as dartus tunic. Scrotum is divided internally into two chambers by a partition called as septum scroti.
ix) Accessory glands: These include a pair of seminal vesicles, prostate gland, and a pair of Cowper’s glands or bulbourethral glands.
a. Seminal Vesicles: these are elongated, coiled sacs about 4 cm long, located near the ampulla of the vas deference. Seminal vesicle contribute a yellowish, slightly alkaline viscous seminal fluid that contains the sugar fructose, a coagulating enzyme, ascorbic acid and prostaglandins.
b. Prostate gland: The prostate gland surrounds the first portion of the urethra. It is large, chestnut shaped, lobulated and spongy gland. It secretes thin, milky, slightly acidic fluid, which is discharged into prostatic part of urethra. It contains citrate, and anticoagulant enzymes.
c. Cowper’s glands: Cowper’s gland also called as bulbourethral gland lie below the prostate gland. They are about the size of pea seeds and secrete alkaline mucus which is discharged into membranous part of urethra. The mucus coats urethra before the sperms are released.
Female Reproductive system
Female reproductive system consists of a pair of ovaries, oviducts, uterus, vagina, external genitalia and mammary glands.
1) Ovaries: ovaries are a pair of primary sex organs of female. These are about a size and shape of almond. They are about 3 cm long, 2 cm wide and 1 cm thick. Ovaries lie in the lower abdomen held to the broad ligament by double folds of peritoneum, the mesovaria. Each ovary is connected to the uterus by ovarian ligament and to the lateral pelvic wall by suspensory ligaments.
Ovaries are solid organs and are composed of connective tissue, The stroma, wrapped by a layer of cuboidal cells, the germinal epithelium, followed by a layer of flattened cells, the visceral peritoneum. The stroma consists of outer cortex and central medulla. The ovarianmedulla contains various rounded bodies called as ovarian follicles. Each follicle contains an ovum surrounded by various layers of follicular cells. The follicle cells of a mature follicle secrete estrogen into the blood. Once in a month, most mature ovum from one ovary is released. The ovarian cortex contains young and mature follicles. There are millions of primary follicles present in the ovary out of which only 60,000-80,000 follicles remain in the ovary at the time of puberty. For becoming a mature (Graafian) follicle a primary follicle undergoes various changes to pass secondary follicle, and tertiary follicle stages.
Ovarian follicles: They are oocyte containing complexes which occur in denser part of cortex. The number of primary follicles in each ovary of a young adult female is about 60,000-80,000. Among this large number of primary follicles only 450 follicle become mature during the whole reproductive span. While others degenerate. The degeneration of follicles is also called as follicular atresia.
Ovarian follicle contains a secondary oocyte covered by granulosa cells and theca cell layers. Granulosa cells are derived from germinal epithelium while as theca develops from the cells of cortex. Theca gets differentiated into outer theca externa andinternal theca interna. Granulosa cells secrete a fluid called as liquor folliculi which creates a large cavity called as antrum. It shifts the oocyte to one side. A stalk or pedicel develops between oocyte and granulosa layer. This stalk is called as cumulus oophorus. Cells surrounding the oocyte elongate radially and form a layer called as corona radiata. Oocyte which is covered by a plasma membrane called as oolemma. Outer to oolemma there is a non-cellular glycoprotein layer called as Zona pellucida. Both zona pellucida and oolemma contain receptor proteins.
During ovulation a ovum gets detached from Graafian follicle and leaves the ovary which is later on taken up by the infundibulum of oviducts.
2) Fallopian tubes or Oviducts: They are a pair of muscular tubes of about 10-12 cm length which lie horizontally in peritoneal cavity above and behind the urinary bladder. Oviduct had four main parts viz Infundibulum, Ampulla, Isthmus, and uterine part.
Infundibulum: It is a funnel shaped fimbriated free end of the oviduct. There is a central pore called as ostium. Margin of fimbriated part of oviduct contains finger like processes called as fimbriae for catching released ovum.
Ampulla: It is curved, dilated part of the oviduct. The lumen of which has a network of plicae.
Isthmus: It forms a straight part of oviduct which connects ampulla with the lateral part of uterus. Lumen of isthmus is narrow. Fertilization of ovum occurs at the junction between Isthmus and Ampulla.Uterine part: It is the part of oviduct which passes into uterus. It is about 1 cm long and controls passage of ovum through muscular movements.
3) Uterus: It is an inverted pair shaped large part of the female reproductive system also called as womb which is specialized for enchoring and nourishing the developing foetus. Uterus is supported in its position by ligaments that attach it to pelvis. It is anteflexed at right angles to the vagina above and behind the urinary bladder in the area of rectum. The size of empty uterus is about is 7.5 cm in length, 5 cm in breadth, and 2.5 cm in thickness.It enlarges to over 100 times during pregnancy in order to accommodate the foetus amniotic fluid surrounding it. Uterine wall is thick and muscular. It is differentiated in to three main layers viz endometrium, myometrium and perimetrium.
Endometrium has two parts, epithelium and lamina propria. Epithelium lines the luminal surface of the uterus. It contains two types of columnar cells, ciliated and secretory. Lamina propria contains connective tissue with fibroblasts, tubular glands, and blood vessels. Endometrium shows cyclic changes during menstrual cycle. It is later on regenerated. Myometrium undergoes strong muscular contractions during delivery of a baby. Perimetrium is outer most layer of the uterus.
Uterus is differentiated into three main regions viz fundus, body and cervix.
Fundus is the upper dome shaped part of the uterus which lies above the level of entry of oviducts. Body is the main part of uterus. It is broad towards the fundus and narrower towards the cervix. Theregion of entry of oviducts is called as cornua. Cervix is the small narrow, cylindrical inferior extremity of the uterus which is about 2.5 cm in length. Along with the vagina, cervical canal is also called as birth canal.
4)Vagina: It is an elastic tube about 8-10cm in length which functions as female copulatory organ, pathway for menstrual flow and birth canal it opens outside into the vestibule through an aperture called as vaginal orifice. Internally vagina contains two longitudinal ridges and a number of transverse rugae. In virgins vaginal orifice is partially covered by a thin membrane called hymen.
5)External genitalia: they are external structures associated with the passage of female genital tract. There is central depression called as vestibule. The sides contain folds called as labia. Some other parts associated are as:
a. Mons pubis: It is anterior rounded fleshy prominence present in the region of pubic symphisis. Skin of this area contains pubic hairs.
b. Perineum : It is an area between vestibule and anus.
c. Clitoris: It is an erectile finger like organ present below Mons pubis at the anterior tip of vestibule above urethral opening at the upper junction of two folds of labia minora. A small sensitive tubercle of erectile tissue occurs at the tip of clitoris which is called as glans clitoridis. It is covered by prepuce.
d. Vestibule : It is the depression present in the region of vulva which contains clitoris and two openings, vaginal orifice and urethral orifice.
e. Labia minora : They are a pair of narrow fleshy folds present around the vestibule devoid of hair but contain sebaceous glands.
f. Labia majora: They are a pair of large thicker fleshy folds which lie on sides of vestibule outside the labia minora from mons pubis to perineum.
6)Associated glands: Human female reproductive tract is not having so much glands. The vaginal glands are Bartholin’s gland or tubulo-alveolar glands located in the lateral walls of vestibule. They secrete a lubricative mucus at the time of copulation
Gametogenesis” is derived from two Greek words, “gametos” meaning gamete and “genesis” meaning formation. So gametogenesis is the process in which male and female gametes are formed inside the living body. Gamete cells are exclusively haploid which means that they contain only half number of chromosomes. Whereas the cells from which gametes are formed are diploid i.e. they have double set of chromosomes. Therefore the gametogenesis involves the reduction division also called as meiosis. Gametogenesis occurs in the gonads. Gametogenesis may be categorized into spermatogenesis and oogenesis based upon the type of gamete formed. Gametogenesis occurs in main three phases viz Multiplication Phase, Growth phase and maturation phase.
Spermatogenesis: It is the process in which haploid spermatozoa are formed inside the testes of male. It beginsduring puberty at the age of 13-14 years approximately and continues throughout the life of an individual. Inside the testes actual process of spermatogenesis occurs in the seminiferous tubules. These seminiferous tubules are lined by germinal epithelium which consists of cuboidal primary germ cells and tall somatic nurse cells.
For the convenience of students spermatogenesis which actually is continuous, is divided into two main stages viz Formation of Spermatids from germ cells and formation of sperms from spermatids.
1) Formation of spermatids :
Spermatids are formed from the undifferentiated germ cells under three main processes. Which are as follows:
a) Multiplication Phase:
Figure Gametogenesis
The undifferentiated cells of germinal epithelium covering seminiferous tubules are called as Sperm mother cells or Spermatogonia. They are formed by mitotic divisions of primary germ cells of germinal epithelium. Spermatogonia have prominent nuclei that contain diploid number of chromosomes. Spermatogonia undergo repeated mitosis to increase their number for further spermatogenesis.Growth: On the sexual maturity of an individual, some Spermatogonia stop dividing and get enlarged in size by accumulating cytoplasm and replicating DNA. These cells hence formed are called as primary spermatocytes. As the spermatocytes are formed in this phase, growth phase is called as spermatocytogenesis. Spermatocytes are double the size of Spermatogonia.
c) Maturation phase: primary spermatocytes formed in the growth phase undergo first meiotic division and produce secondary spermatocytes. This division is reductional as the number of chromosomes is reduced to half. Secondary spermatocytes soon undergo second meiotic division giving rise to spermatids. This division is equational as the number of chromosomes is not reduced further.
In the meiotic division where secondary spermatocytes and spermatids are formed, daughter cells are not completely divided rather remain interconnected with one another. But this interconnection is not shown in diagrams for the sake of simplicity.
2) Formation of spermatozoa from spermatids: Spermatids formed in the first phase do not divide further rather they get metamorphosed into sperms by certain modification. Spermatogonia, thus produces four spermatozoa. This process of spermatids into spermatozoa is also called as spermiogenesis.
Spermiogenesis involves movement of some organelles to some specific positions, certain changes in organelles, water content, cytoplasm and Golgi apparatus. Formation of a complete sperm cell takes about a couple of months.Structure of spermatozoa
A spermatozoa is a haploid gamete cell which has four main
parts: head, neck, middle pieces and tail. Head is flat and
oval. It is composed of a large nucleus and a small anterior
acrosome. Nucleus contains mainly DNA and some proteins.
Acrosome is formed of Golgi apparatus. It contains
hydrolytic enzymes, and is used to penetrate the egg during
fertilization.
Neck is very short
and containing two
centrioles one
behind and at right
angle to another.
Proximal centriole
plays a key role in
cleavage of zygote
while the distal
centriole gives rise
to the axial filament and tail of the sperm.
Middle piece is cylindrical. It contains mitochondria coiled
round the axial filament. Mitochondria provide energy to the
sperm for the movement within the female genital tract.
Tail is very long and tapering and if formed of cytoplasm.Entire sperm is covered by a plasma membrane. The
spermatozoa swim by vibrating their tail in a fluid medium
in search of ova.
Oogenesis:
Oogenesis is the process in which ova are formed in the
female gonads. It occurs within the ovaries. Egg formation
begins before birth but is completed after fertilization. It
consists of three main phases viz Multiplication phase,
growth phase and maturation phase.
i) Multiplication phase: Certain cells in the germinal
epithelium of the ovary are larger than other and also
have larger nuclei. These larger cells undergo mitosis
divisions producing germ cells called as oogonia or egg
mother cell. Oogonia contain double number of
chromosomes. Oogonia undergo further mitotic divisions
and project into the stroma as a cord called egg tube of
Pfluger. It later on becomes a mass of cells called as egg
nest. One cell in the egg nest grows and becomes primary
oocyte. Other cells in the egg nest lose the tendency to
become primary oocyte and form a layer of cells called as
follicular epithelium around the oocyte in order to protect
and nourish it. The structure which is now formed is
called as primary follicle, which sinks into the stroma.
Primary oocyte remains in meiosis I until just before
ovulation in an adult female.ii) Growth phase: Growth phase of primary oocyte is
very long, extending over many years. Its cytoplasm
increases and nucleus enlarges.
iii) Maturation Phase: A full grown primary oocyte
undergoes first meiosis producing two daughter cells,
one of which is extremely small while other is as large
as primary oocyte itself. The larger cell is called as
secondary oocyte. It receives almost all the cytoplasm
of the parent cell. The smaller cell is termed as first
polar body. Secondary oocyte starts undergoing
second meiosis which is arrested in metaphase. This
is the second resting stage which is resumed only
after the sperm entry. After the fertilization meiosis II
is resumed, and again gives rise to a small cell called
second polar body and a large cell termed as ootid.
Ootid further grows into a functional haploid ovum.
Development of ovum takes about 13 years. Polar
bodies soon distintigrade.
Ovulation refers to the release of ovum from the ovary. In
human beings it occurs about 14 days before next
menstruation. Mature follicle is lighter and rises to the
surface of ovary, causing a bulge in the ovary. Follicular and
ovarian walls rupture to release the egg.
Reproductive cycle is mainly of two types viz oestrous cycle
and menstrual cycle.
Oestrous cycle: Oestrous cycle consists of few days oestrous
or heat followed by anaestrous or quiescence. During the
heat phase female is more responsive to the sexual act. In
this stage eggs are released and fertilization is possible. On
the other hand in anaestrous phase female becomes passive
and does not accept the male. In some seasonally breeding
mammals oestrous phase prolongs throughout the breeding
season.Menstrual cycle: Menstrual cycle has been divide into three
main phases including Menstrual phase, Follicular phase,
and luteal phase.
Menstrual phase: This phase of the female
reproductive cycle is also called as weeping of uterus or
funeral of ova. Commonly it is also termed as menses or
bleeding phase. It lasts for 3-5 days. During this phase
endometrial wall of the uterus is cut off and passes out of the
vagina along with blood, serous fluid and mucosal fragments.
The total quantity is about 75-100 ml. Menstrual blood
usually does not clot due to the presence of fibrinolysin.
Menstrual phase of the menstrual cycle occurs when the
level of gonadotropin and other ovarian hormones is low.
Follicular phase/ proliferative phase/ estrogen
phase: reduced level of gonadotropin and ovarian hormones
stimulate hypothalamus to produce GnRH(Gonadotropin
Releasing hormone). It activates anterior pituitary to
produce gonadotropins. In presence of FSH about 12 ovarian
follicles begin to proliferate granulosa cells , enlargement of
follicles, addition of thecal covering on outer side and
development of cavity called as antrum.’
Granulosa cells secrete estrogen and small quantity of
inhibin. After about a week of development only a single
ovarian follicle becomes a mature Graafian follicle and
others start degenerating. In presence of FSH granulosa cellsdevelop LH receptors. After the stoppage of menstruation
first two days of proliferative phase are spent in re-
epithelialization of endometrium and repair of ruptured
blood vessels. It is followed by growth and thickening of
endometrium for next 7-9 days. During this time period new
blood capillaries develop, uterine glands elongate and get
coiled. Epithelium of oviduct develop more cilia. Secretory
cells become enhanced in their activity. Muscles of genital
tract become more active. Cervix develops mucus strings
forming channels for guiding sperm movements.
Towards the end of this phase endometrium becomes
about 3mm thick. By the time there is increased binding of
LH to the granulosa cells. High levels of estrogen and LH
causes rapid growth of follicles and radial elongation of
corona cells, so that the attachment of corona cells with rest
of the follicular cells weakens. Graafian follicles rise to the
surface of the ovary producing a stigma. Stigma ruptures and
ovum with corona radiata is released out into the viscous
fluid. This process is called as ovulation. It occurs roughly in
the middle of menstrual cycle.
Luteal phase or secretory phase: This is the third phase of
menstrual cycle and it extends for 12-14 days. Phase starts
after ovulation. The changes occurring in the female
reproductive tract during the luteal phase are studied undertwo separate headings viz changes in endometrium and
corpus luteum.
Corpus luteum: Under the influence of LH Graafian
follicle which is now devoid of ovum, continues growth.
Follicular cells are converted into the lutein cells. This
phenomenon is called as lutenization. Ruptured Graafian
follicle is now called as corpus luteum. It secretes
progesterone, estrogen and inhibin.
Changes in endometrium: LH and progesterone help
in growth of endometrium and its thickening. Endometrial
glands become secretory. Thickening of endometrium
increased about 5-6mm. Uterine wall becomes ready for
enchoring and nourishing the developing foetus.
Progesterone inhibits the uterine movements and growth of
new follicles.
However when there is no fertilization, high level of LH
and inhibin reduces the GnRH production. Due to which
levels of LH and FSH fall. Reduced level of LH results in
reduced secretion of progesterone. By all these changes in
hormone levels corpus luteum is converted into corpus
albicans.
Process in which fusion of haploid male gamete and haploid female gamete occurs is termed as fertilization. In humanbeings fertilization is internal as in other mammals. It fertilization cone. Sperms thus enter the egg. Distal
centriole splits into two centrioles to generate mitotic
spindles for cell division.
d) Karyogamy/Amphimixis : Sperm entry stimulates the
egg to resume and complete the suspended meiosis II.
This produces a mature haploid ovum and a secondary
polar body. At this time sperm head separates from
middle piece and tail, and becomes the male pronucleus.
Polar body and tail sooner degenerate. Chromosomes
od egg are not organized into a nucleus. They represent
female pronucleus. Chromosomes of sperm are set free
by breaking down the nuclear envelope. Two sets of
chromosomes go over a spindle formed between the
centrioles. Mixing up of chromosome sets of ovum and
sperm is called as Amphimixis or Karyogamy. This
completes the process of fertilization. It combines the
genetic information from two parents. Ovum is now a
diploid cell termed as zygote. Mother is now said to be
pregnant.usually takes place at the junction of isthmus and ampulla.
Fertilization can be well understood only by understanding
all its events separately. Events involved in fertilization are
as under:
Arrival of sperms: Mammalian male discharges sperms
high up in the vagina of female close to the cervix during the
process called coitus. This process is also called as
insemination. From vagina sperms reach the ampulla of
uterus partially by its own effort and partially by uterine
action.
Sperm’s effort: spermatozoa present in the semen travel
a long way through the uterus into the fallopian tube by
swimming in the fluid medium. Sperms may swim at very
low speed of about 1.5-3mm per minute. A single ejaculate
which is approximately about 3-5 ml in volume contains
200-400 million sperms. However some publications write it
as 80-100 million sperms. Among the millions sperms only
100 may reach the oviducts.
Role of uterus: certain activities of the female reproductive
tract help sperms to reach the fertilization spot. For instance
contractions of uterus or fallopian tubes propel the sperms
upward. Sperms may reach the fallopian tubes within five
minutes. Although a sperm can survive in the femalereproductive system for about 1-3 days, it can fertilize the
egg in 12-24 hours following ovulation.
Arrival of egg: the egg released from the Graafian
follicle is in the stage of secondary oocyte. It is received by
nearby fallopian funnel and sent in the oviduct by the
movement of fimbriae and their cilia. An oocyte can live for
about 72 hours but can be fertilized within 24 hours. Most of
the sperms which come close to the oocyte contribute
enzymes which disrupt the follicular cells still investing the
egg. Only one sperm succeeds in fertilizing the egg.
Capacitation of sperms: Sperms in the female
reproductive tract is activated to be capable of fertilizing an
egg by secretions of female genital tract. These secretions
alter or remove certain molecules deposited on the surface
of spermatozoon from the semen. This process is called as
capacitation of sperms. It takes about 6 hours.
Secretions of prostate gland, seminal vesicles, and
Cowper’s gland contain nutrients which activate the sperms
and substances that neutralize the acidity in the vagina.
Sperms need an alkaline medium in order to be motile.
Capacitation develops by suppression of decapacitation
factors. It occurs by following processes.
1) Dilution of inhibitory factors present in semen.2) Washing of cholesterol vesicles covering the sperm
head.
3) Removal of membrane cholesterol of the acrosome. This
weakens the sperm covering.
4) Entering of Ca2+ into the sperm. This changes the
movement of sperm tail from slower undulating motion
to fast whiplash motion.
Physical and chemical events involved in fertilization:
a)Acrosome reaction: secondary oocyte reaching the
oviduct is covered by zona pellucida and corona radiata.
A capacitated sperm enters the corona radiata to reach
the zona pellucida. One of three glycoproteins (ZP1,
ZP2, ZP3) ZP3 functions as sperm receptor and binds
with the complementary molecule on the sperm head. It
induces the sperm to release its hydrolytic enzymes
collectively called as sperm lysins.
These sperm lysins are as:
i) Hyaluranidase: this is the enzyme which
hydrolyses the hyaluronic acid of follicular cells. It
also dissolves the cementing material between the
follicular cells leading their separation.
ii) corona penetrating enzyme: This is the enzyme
which dissolves the corona radiata layer around the
oocyte by hydrolyzing their ground substances.iii) Acrosin or zona lysin: This is the enzyme which
helps in the digestion of zona pellucida. This process
is also called as compatibility reaction. By this
reaction there is also the formation of an outgrowth
called as fertilization cone. It occurs by the special
proteins present on the zona pellucida and sperm
surface. These proteins are termed as fertilizin and
anti-fertilizin.
Optimum PH, Ca2+ and Mg 2+ concentration is also
important for the acrosomal reaction.
b)Cortical reaction: Soon after the fusion of sperm and egg
membranes egg shows the cortical reaction to prevent
entry of more than one sperms. Due to the contact
between sperm head and fertilization cone, Ca 2+ wave is
initiated which causes extrusion of cortical granules out
of the egg. They bring about the modification of plasma
membrane and change it into fertilization membrane or
activation calyx. It does not allow the other sperms to
enter the egg.
Cortical granules actually release their enzymes
between plasma membrane of oocyte and zona
pellucida. These harden the zona pellucida to become
a barrier for other sperms.
c) Sperm entry: as discussed earlier ovum extends finger
like microvilli around the entering sperm to form fertilization cone. Sperms thus enter the egg. Distal
centriole splits into two centrioles to generate mitotic
spindles for cell division.
d) Karyogamy/Amphimixis : Sperm entry stimulates the
egg to resume and complete the suspended meiosis II.
This produces a mature haploid ovum and a secondary
polar body. At this time sperm head separates from
middle piece and tail, and becomes the male pronucleus.
Polar body and tail sooner degenerate. Chromosomes
od egg are not organized into a nucleus. They represent
female pronucleus. Chromosomes of sperm are set free
by breaking down the nuclear envelope. Two sets of
chromosomes go over a spindle formed between the
centrioles. Mixing up of chromosome sets of ovum and
sperm is called as Amphimixis or Karyogamy. This
completes the process of fertilization. It combines the
genetic information from two parents. Ovum is now a
diploid cell termed as zygote. Mother is now said to be
pregnant.
Early embryo development or embryogenesis is the
development of embryo fertilized ovum and its subsequent
development into young organism. It has three major stages;
cleavage, gastrulation and organogenesis.
Cleavage: It is a series of mitotic divisions of zygote
following fertilization forming a blastula.
Difference between cleavage and ordinary mitosis: The
cleavage is basically mitosis producing diploid cells. They
differ from typical mitosis in a few points:
1)Divisions occur in quick succession.
2)Interphase in cleavage is short and does not
involve growth so that the resulting blastomeres
become smaller in size and their number
increases.
3) DNA synthesis occurs faster in cleavage to
facilitate the duplication of chromosomes for the
rapidly forming new blastomeres.
4)Shape of embryo does not change during cleavage
because there is no movement of blastomeres.
5)Oxygen consumption generally increases during
cleavage to provide adequate energy for activities
taking place in rapid cell division.
In nutshell
during cleavage,
the cell
undergoes
mitosis and
synthesis phase
of cell cycle but
they skip growth
phases.
Cleavage in human zygote: It occurs during the passage of
zygote through the oviducts to the uterus. It is holoblastic i.e.
it divides zygote and blastomeres completely into daughter
cells. However blastomeres differ in size from the start. This
number does not increase by simply doubling the sequence
as occurs in frog. First cleavage occurs about 30 hours after
fertilization. It occurs along animal-vegetal pole axis. It
produces two blastomeres, one slightly larger than the other.The two blastomeres remain adhered to one another. The
second cleavage occurs within 60 hours after fertilization. It
is at the right angle to the plane of first division and divides
each blastomere into two. The larger blastomere divides a
little bit sooner as compared to smaller one so there is an
intermediate 3-cell stage before the characteristic 4-cell
stage. Third
cleavage occurs
72 hours after
fertilization.
Morula
stage: Cleavage
division
produces a ball
of cells called as
morula. It has 8-
16 cells,
occasionally 32
cells may also be
present. It is still
covered by zona pellucida. It undergoes compaction. It
actually means tightly adhering of blastomeres due to the
formation of proteins called as cohesions.
Outer peripheral cells are flatter, smaller and with tight
junctions. Inner cell mass contains slightly larger roundedcells with gap junctions. Morula does not remain in the
ampulla part of oviduct but slowly descends towards the
uterus in 4-6 days. The descent is caused due to the feeble
fluid current produced by secretory and ciliary activity
mucoidal epithelium. During this period corona radiata
detaches.
Significance of Cleavage:
i) It converts unicellular zygote into a multicellular
embryo.
ii) It is rapid cell division and daughter cells do not need
to grow before the next division.
iii) There occurs reduction in cell size.
iv) Non development of cell junctions is seen which helps
in rearrangement of cells.
Formation of Blastula: outer layer of cells of morula now
absorbs the nutritive fluid secreted by the uterine mucus
membrane (also called as
uterine milk), enlarge and
flatten further to form
trophoblast or
trophoectoderm.
Trophoblast secretes
a fluid into the interior
creating a cavity called as Blastocoel. But it is to be noted here that according to
various publications this fluid is not secreted by trophoblast
cells rather it is absorbed from uterine secretions by
trophoblast cells.
As the quantity of fluid increases, the morula enlarges
rapidly and assumes the size of a cyst. It is then called as
Blastocyst.
Now, inner cell mass looks like a knob at one pole. The
knob gives rise to the embryo hence called as embryonal
knob. The side of the blastocyst to which embryonal knob is
attached is called as embryonic pole or animal pole. The
trophoblast does not take part in formation of embryo
proper. It remains external to the embryo and gives rise to
extra embryonic membranes viz chorion, allantois, yolk sac
and amnion for the protection and nourishment of embryo.
Trophoblast cells in direct contact with embryonal knob are
called as cells of rauber.Implantation: Blastocyst contains outer trophoblast
and inner cell mass. Inner cell mass gives rise to the embryo
while as trophoblast gives rise to the extra embryonic
membranes viz chorion, amnion, allantois and yolk sac.
During implantation blastocyst is attached to and buried into
endometrium of uterus. But it should not be implanted on
wrong site. Wrong implantation is prevented by zona
pellucida.While moving through the oviduct towards uterus,
blastocyst expands within zona pellucida. Trophoblast cell
membranes contain Na+/K+-ATPase also called as sodium-
potassium pump facing the blastocoel. These ATPase
complexes pump Na+ ions into blastocoel which in turn
causes osmosis of water into blastocoel cavity, thus
enlarging blastocoel. During this time zona pellucida
prevents the attachment of blastocyst to oviduct walls. If
blastocyst is attached to the oviduct walls, it will cause tubal
pregnancy or ectopic pregnancy. It is a dangerous condition
which may cause life threatening hemorrhage.
Mammalian blastocyst hatches from the zona pellucida
by lysing a small hole as the blastocyst expands. Once out the
blastocyst can make direct attachment to the uterus.
Sometimes during the process while a blastocyst is coming
out of zona layer it may break into two blastocysts which
causes the formation of monozygotic (identical) twins. Pregnancy and embryonic development:
Pregnancy is a
condition of having developing embryo or foetus inside the womb of the
mother. Soon after the implantation, the surface cells of the
trophoblast secrete lytic enzymes which cause erosion of
endometrium. They also give rise to outgrowths called as
chorionic villi. Chorionic walls and uterine walls become
interdigitated. The villi not only help in attachment but also
in absorbtion of nutrients.
Uterine tissue undergoes nutrient enrichment, enlargement
and formation of uterine part of placenta called as decidua.
Decidua has three regions viz decidua basalis, decidua
peritalis, and decidua capsularis.
Trophoblast covering secretes a hormone called as
Human Chorionic Gonadotropin (HCG). Hormone can be
detected in urine of gravid woman within a day or so after
implantation.It helps in secretion of progesterone inorder to
prevent menstruation. Progesterone induces the cervical
glands to secrete viscous mucus for filling the cervical canal
to form a protective plug. Therefore progesterone is also
termed as pregnancy hormone.
Gastrulation:
During blastocyst formation there was the formation of
embryonal knob which soon shows rearrangement to form
an embryonic disc also called as bilaminar disc.During gastrulation, movement of cells occurs in small
masses or sheets so as to
form primary germ layers.
There are three germ layers
in mammalian embryo viz
ectoderm, mesoderm and
endoderm. These cell
movements are also called as
morphogenetic movements.
Production of gastrulation is a
ball of cells called as gastrula
which is different from
blastocyst in various characteristics.
Formation of primary germ layers:
inner cell mass or embryonal knob possesses the stem cells
which have a tendency to form all types of tissues and
organs. Normally they get rearranged to form a flat disc
called as embryonic disc or germinal disc. It differentiates
into two layers outer epiblast of larger columnar cells and
inner smaller cuboidal hypolast. Hypoblast functions as
embryonic endoderm. It is the first germinal layer to
differentiate.Hypoblast grows on the sides and forms a covering over the
blastocoel. This converts the blastocoel into primary yolk
sac. Meanwhile trophoblast of the region grows to form
extra embryonic mesoderm.it splits up and forms extra
embryonic coelom.it compresses the primary yolk sac.
Secondary smaller yolk sac is thus formed. Simultaneously
embryonic endoderm forms a tube of its own. This is the gut
of the embryo.
Most of the epiblast grows laterally to produce
ectoderm. However at one point epilast cells proliferate to
form a first cellular elevation called primitive streak. Cells of
primitive streak continue to proliferate and pass out in
between epilast and hypoblast forming third germ layer
called as mesoderm.
Formation of
extra embryonic
membranes:
Need for foetal
membranes:
Embryo of an aquatic organism is surrounded by water,
which protects
the embryo, keeps
it moist, removes
waste and
permits gaseous
exchange. In
terrestrial
vertebrates these
all functions are
taken up by
embryonic
membranes, some of which take part in the formation of
placenta in
mammals. The
placenta
develops
before emryo
and because
embryo
depends upon
it.Four
extra embryonic membranes are as:
1)Yolk sac
2)Amnion
3)Chorion
4)Allantois
Yolk sac: It is formed below the embryo. It contains fluid
but not yolk. Yolk sac is vestigial organ inherited from avian
ancestors. We have almost discussed how primary and
secondary yolk sacs were formed. Yolk sac becomes the site
of blood cell formation until the function is taken up by liver
at about 6th week of gestation. Therefore yolk sac begins to
shrink.
Amnion: It is formed above the embryo. It consists of
trophoblast and mesoderm. It encloses a fluid filled space
called as amniotic cavity. Amnion and amniotic cavity
enlarge and hence cover the entire embryo. Embryo is
suspended in amniotic cavity by an umbilical cord. Umbilical
cord is forms of stalks of yolk sac and allantois. The main
blood vessels from placenta reach the foetus through
umbilical cord.
According to some authors actual origin of amniotic
fluid is not properly known however it can be of dual origin
i.e. foetal as well as maternal. Some authors believe that it is
derived from foetal kidneys and urinary bladder. In much
simpler terms amniotic fluid is derived from foetal urine. It
is completely replaced every 24 hours.
Functions of amniotic fluid:
1)It cushions the embryo protecting it from mechanical
shocks, injuries and stress because of maternal organs.
2)It permits foetal movement.
3)It prevents bacterial infections.
4)It maintains a constant pressure and temperature.
Allantois: It is a small membranous sac that is pushed out
from the gut. It remains small and does not reach chorion. It
forms the arteries and veins to vascularize the chorion. It
also forms the blood cells. Due to presence of allantois
human placenta is called as Allantochorionic.
Chorion: it is the outer most foetal membrane and
surrounds the foetus completely. It is covered by mesoderm
and trophoblast. It protects the embryo and forms the
placenta for metabolic exchange between foetus and mother.
Human placenta:
It is a foeto-maternal connective that develops during
pregnancy and forms a temporary association between
maternal and foetal tissues for supporting the foetus during
its development. Foetus is connected with the placenta by a
long flexible string called as umbilical cord. It is mainly
formed of allantois and is covered by amniotic epithelium.
Cord contains two arteries and a single vein. Arteries
transport deoxygenated blood from foetus while as veintransports oxygenated blood to the foetus. Human placenta
is deciduate which means that it is passed out at the time of
parturition. Though the placenta is first developed all
around the embryo but later on it remains restricted into a
disc shaped area, so it is called as metadiscoidal placenta. It
is also called as chorionic placenta because it is mainly
derived from chorion. It also contains few parts derived
from allantois. Decidua basalis contains some blood sinuses
into which the blood vessels of chorionic villi are immersed.
In the region of contact, the epithelium, connective tissue
and endothelial linings are corroded. Only the foetal barriers
present over the blood vessels persist. Such a placenta is
called as haemochorial placenta.
Functions of placenta:
1)Foetus receives all the nutrients from maternal blood
via placenta. The transfer occurs through the diffusion
and active transport.
2)Placenta helps in the exchange of respiratory gases.
3)Placenta stores fat and glycogen which can e broken
down and absorbed by foetus.
4)Foetus excretes its toxic wastes through placenta.
5)Maternal antibodies enter the foetus through placenta
which protects foetus from various diseases and
disorders.
6)Placenta does not allow any pathogen or toxic materials
to enter the foetal circulatory system.
7) Placenta is an important endocrine gland that produces
a number of hormones, which are discussed as follows:
i) Human Chorionic Gonadotropin: its secretion starts
immediately after the implantation. The hormone
acts upon corpus decidua just as LH, causes it to
grow and maintain it for long term pregnancy. They
prevent menstruation, stimulate the endometrium to
grow and store nutrients, and cervix to plug the
passage by viscous secretions. It also acts on male
foetus’s testes, stimulating the secretions of
testosterone and development of male sex organs.
ii) Chorionic thyrotrophin: it stimulates mothers thyroid
gland for producing more hormones.
iii) Chorionic corticotrophin: it acts on adrenal glands of
mother to stimulate the secretion of hormones.
Increased secretion of aldosterone helps the mother
to retain sodium hence more fluid in the body. It
occasionally leads to the pregnancy hypertension in
the mother.
Placenta may also secrete corticotrophin
releasing hormone (CRH) which may
determine the timing of parturition as excess
of it has been found to cause prematuredelivery while as its lower level delays the
child birth.
iv) Human Placental lactogen: The hormone functions as
weak growth hormone. It stimulates growth of
breasts. It decreases insulin sensitivity of mother so
that the mother in unable to utilize more glucose.
Hence the glucose become s available for foetus.
v) Progestogens: progestogen helps in maintaining
pregnancy, decreasing contractility of uterus, growth
of endometrium etc. It is because of its importance in
maintaining pregnancy that it is called as pregnancy
hormone.
vi) Estrogen: placenta converts adrenal androgen of
mother and foetus into the estrogen. The hormone
help in enlargement of pregnant uterus, enlargement
and growth of breasts, growth of mothers external
genitalia besides relaxing pelvic ligaments.
vii) Relaxin: it is secreted both y corpus luteum and
placenta. The hormone softens the connective tissue
of symphisis pubica for reducing discomfort of
carriage, and facilitating easy child birth. It also
dilates cervix and loosenes the ligaments of
Spermatogenesis: It is the process in which haploid spermatozoa are formed inside the testes of male. It beginsduring puberty at the age of 13-14 years approximately and continues throughout the life of an individual. Inside the testes actual process of spermatogenesis occurs in the seminiferous tubules. These seminiferous tubules are lined by germinal epithelium which consists of cuboidal primary germ cells and tall somatic nurse cells.
For the convenience of students spermatogenesis which actually is continuous, is divided into two main stages viz Formation of Spermatids from germ cells and formation of sperms from spermatids.
1) Formation of spermatids :
Spermatids are formed from the undifferentiated germ cells under three main processes. Which are as follows:
a) Multiplication Phase:
Figure Gametogenesis
The undifferentiated cells of germinal epithelium covering seminiferous tubules are called as Sperm mother cells or Spermatogonia. They are formed by mitotic divisions of primary germ cells of germinal epithelium. Spermatogonia have prominent nuclei that contain diploid number of chromosomes. Spermatogonia undergo repeated mitosis to increase their number for further spermatogenesis.Growth: On the sexual maturity of an individual, some Spermatogonia stop dividing and get enlarged in size by accumulating cytoplasm and replicating DNA. These cells hence formed are called as primary spermatocytes. As the spermatocytes are formed in this phase, growth phase is called as spermatocytogenesis. Spermatocytes are double the size of Spermatogonia.
c) Maturation phase: primary spermatocytes formed in the growth phase undergo first meiotic division and produce secondary spermatocytes. This division is reductional as the number of chromosomes is reduced to half. Secondary spermatocytes soon undergo second meiotic division giving rise to spermatids. This division is equational as the number of chromosomes is not reduced further.
In the meiotic division where secondary spermatocytes and spermatids are formed, daughter cells are not completely divided rather remain interconnected with one another. But this interconnection is not shown in diagrams for the sake of simplicity.
2) Formation of spermatozoa from spermatids: Spermatids formed in the first phase do not divide further rather they get metamorphosed into sperms by certain modification. Spermatogonia, thus produces four spermatozoa. This process of spermatids into spermatozoa is also called as spermiogenesis.
Spermiogenesis involves movement of some organelles to some specific positions, certain changes in organelles, water content, cytoplasm and Golgi apparatus. Formation of a complete sperm cell takes about a couple of months.Structure of spermatozoa
A spermatozoa is a haploid gamete cell which has four main
parts: head, neck, middle pieces and tail. Head is flat and
oval. It is composed of a large nucleus and a small anterior
acrosome. Nucleus contains mainly DNA and some proteins.
Acrosome is formed of Golgi apparatus. It contains
hydrolytic enzymes, and is used to penetrate the egg during
fertilization.
Neck is very short
and containing two
centrioles one
behind and at right
angle to another.
Proximal centriole
plays a key role in
cleavage of zygote
while the distal
centriole gives rise
to the axial filament and tail of the sperm.
Middle piece is cylindrical. It contains mitochondria coiled
round the axial filament. Mitochondria provide energy to the
sperm for the movement within the female genital tract.
Tail is very long and tapering and if formed of cytoplasm.Entire sperm is covered by a plasma membrane. The
spermatozoa swim by vibrating their tail in a fluid medium
in search of ova.
Oogenesis:
Oogenesis is the process in which ova are formed in the
female gonads. It occurs within the ovaries. Egg formation
begins before birth but is completed after fertilization. It
consists of three main phases viz Multiplication phase,
growth phase and maturation phase.
i) Multiplication phase: Certain cells in the germinal
epithelium of the ovary are larger than other and also
have larger nuclei. These larger cells undergo mitosis
divisions producing germ cells called as oogonia or egg
mother cell. Oogonia contain double number of
chromosomes. Oogonia undergo further mitotic divisions
and project into the stroma as a cord called egg tube of
Pfluger. It later on becomes a mass of cells called as egg
nest. One cell in the egg nest grows and becomes primary
oocyte. Other cells in the egg nest lose the tendency to
become primary oocyte and form a layer of cells called as
follicular epithelium around the oocyte in order to protect
and nourish it. The structure which is now formed is
called as primary follicle, which sinks into the stroma.
Primary oocyte remains in meiosis I until just before
ovulation in an adult female.ii) Growth phase: Growth phase of primary oocyte is
very long, extending over many years. Its cytoplasm
increases and nucleus enlarges.
iii) Maturation Phase: A full grown primary oocyte
undergoes first meiosis producing two daughter cells,
one of which is extremely small while other is as large
as primary oocyte itself. The larger cell is called as
secondary oocyte. It receives almost all the cytoplasm
of the parent cell. The smaller cell is termed as first
polar body. Secondary oocyte starts undergoing
second meiosis which is arrested in metaphase. This
is the second resting stage which is resumed only
after the sperm entry. After the fertilization meiosis II
is resumed, and again gives rise to a small cell called
second polar body and a large cell termed as ootid.
Ootid further grows into a functional haploid ovum.
Development of ovum takes about 13 years. Polar
bodies soon distintigrade.
Ovulation refers to the release of ovum from the ovary. In
human beings it occurs about 14 days before next
menstruation. Mature follicle is lighter and rises to the
surface of ovary, causing a bulge in the ovary. Follicular and
ovarian walls rupture to release the egg.
Reproductive cycle is mainly of two types viz oestrous cycle
and menstrual cycle.
Oestrous cycle: Oestrous cycle consists of few days oestrous
or heat followed by anaestrous or quiescence. During the
heat phase female is more responsive to the sexual act. In
this stage eggs are released and fertilization is possible. On
the other hand in anaestrous phase female becomes passive
and does not accept the male. In some seasonally breeding
mammals oestrous phase prolongs throughout the breeding
season.Menstrual cycle: Menstrual cycle has been divide into three
main phases including Menstrual phase, Follicular phase,
and luteal phase.
Menstrual phase: This phase of the female
reproductive cycle is also called as weeping of uterus or
funeral of ova. Commonly it is also termed as menses or
bleeding phase. It lasts for 3-5 days. During this phase
endometrial wall of the uterus is cut off and passes out of the
vagina along with blood, serous fluid and mucosal fragments.
The total quantity is about 75-100 ml. Menstrual blood
usually does not clot due to the presence of fibrinolysin.
Menstrual phase of the menstrual cycle occurs when the
level of gonadotropin and other ovarian hormones is low.
Follicular phase/ proliferative phase/ estrogen
phase: reduced level of gonadotropin and ovarian hormones
stimulate hypothalamus to produce GnRH(Gonadotropin
Releasing hormone). It activates anterior pituitary to
produce gonadotropins. In presence of FSH about 12 ovarian
follicles begin to proliferate granulosa cells , enlargement of
follicles, addition of thecal covering on outer side and
development of cavity called as antrum.’
Granulosa cells secrete estrogen and small quantity of
inhibin. After about a week of development only a single
ovarian follicle becomes a mature Graafian follicle and
others start degenerating. In presence of FSH granulosa cellsdevelop LH receptors. After the stoppage of menstruation
first two days of proliferative phase are spent in re-
epithelialization of endometrium and repair of ruptured
blood vessels. It is followed by growth and thickening of
endometrium for next 7-9 days. During this time period new
blood capillaries develop, uterine glands elongate and get
coiled. Epithelium of oviduct develop more cilia. Secretory
cells become enhanced in their activity. Muscles of genital
tract become more active. Cervix develops mucus strings
forming channels for guiding sperm movements.
Towards the end of this phase endometrium becomes
about 3mm thick. By the time there is increased binding of
LH to the granulosa cells. High levels of estrogen and LH
causes rapid growth of follicles and radial elongation of
corona cells, so that the attachment of corona cells with rest
of the follicular cells weakens. Graafian follicles rise to the
surface of the ovary producing a stigma. Stigma ruptures and
ovum with corona radiata is released out into the viscous
fluid. This process is called as ovulation. It occurs roughly in
the middle of menstrual cycle.
Luteal phase or secretory phase: This is the third phase of
menstrual cycle and it extends for 12-14 days. Phase starts
after ovulation. The changes occurring in the female
reproductive tract during the luteal phase are studied undertwo separate headings viz changes in endometrium and
corpus luteum.
Corpus luteum: Under the influence of LH Graafian
follicle which is now devoid of ovum, continues growth.
Follicular cells are converted into the lutein cells. This
phenomenon is called as lutenization. Ruptured Graafian
follicle is now called as corpus luteum. It secretes
progesterone, estrogen and inhibin.
Changes in endometrium: LH and progesterone help
in growth of endometrium and its thickening. Endometrial
glands become secretory. Thickening of endometrium
increased about 5-6mm. Uterine wall becomes ready for
enchoring and nourishing the developing foetus.
Progesterone inhibits the uterine movements and growth of
new follicles.
However when there is no fertilization, high level of LH
and inhibin reduces the GnRH production. Due to which
levels of LH and FSH fall. Reduced level of LH results in
reduced secretion of progesterone. By all these changes in
hormone levels corpus luteum is converted into corpus
albicans.
Process in which fusion of haploid male gamete and haploid female gamete occurs is termed as fertilization. In humanbeings fertilization is internal as in other mammals. It fertilization cone. Sperms thus enter the egg. Distal
centriole splits into two centrioles to generate mitotic
spindles for cell division.
d) Karyogamy/Amphimixis : Sperm entry stimulates the
egg to resume and complete the suspended meiosis II.
This produces a mature haploid ovum and a secondary
polar body. At this time sperm head separates from
middle piece and tail, and becomes the male pronucleus.
Polar body and tail sooner degenerate. Chromosomes
od egg are not organized into a nucleus. They represent
female pronucleus. Chromosomes of sperm are set free
by breaking down the nuclear envelope. Two sets of
chromosomes go over a spindle formed between the
centrioles. Mixing up of chromosome sets of ovum and
sperm is called as Amphimixis or Karyogamy. This
completes the process of fertilization. It combines the
genetic information from two parents. Ovum is now a
diploid cell termed as zygote. Mother is now said to be
pregnant.usually takes place at the junction of isthmus and ampulla.
Fertilization can be well understood only by understanding
all its events separately. Events involved in fertilization are
as under:
Arrival of sperms: Mammalian male discharges sperms
high up in the vagina of female close to the cervix during the
process called coitus. This process is also called as
insemination. From vagina sperms reach the ampulla of
uterus partially by its own effort and partially by uterine
action.
Sperm’s effort: spermatozoa present in the semen travel
a long way through the uterus into the fallopian tube by
swimming in the fluid medium. Sperms may swim at very
low speed of about 1.5-3mm per minute. A single ejaculate
which is approximately about 3-5 ml in volume contains
200-400 million sperms. However some publications write it
as 80-100 million sperms. Among the millions sperms only
100 may reach the oviducts.
Role of uterus: certain activities of the female reproductive
tract help sperms to reach the fertilization spot. For instance
contractions of uterus or fallopian tubes propel the sperms
upward. Sperms may reach the fallopian tubes within five
minutes. Although a sperm can survive in the femalereproductive system for about 1-3 days, it can fertilize the
egg in 12-24 hours following ovulation.
Arrival of egg: the egg released from the Graafian
follicle is in the stage of secondary oocyte. It is received by
nearby fallopian funnel and sent in the oviduct by the
movement of fimbriae and their cilia. An oocyte can live for
about 72 hours but can be fertilized within 24 hours. Most of
the sperms which come close to the oocyte contribute
enzymes which disrupt the follicular cells still investing the
egg. Only one sperm succeeds in fertilizing the egg.
Capacitation of sperms: Sperms in the female
reproductive tract is activated to be capable of fertilizing an
egg by secretions of female genital tract. These secretions
alter or remove certain molecules deposited on the surface
of spermatozoon from the semen. This process is called as
capacitation of sperms. It takes about 6 hours.
Secretions of prostate gland, seminal vesicles, and
Cowper’s gland contain nutrients which activate the sperms
and substances that neutralize the acidity in the vagina.
Sperms need an alkaline medium in order to be motile.
Capacitation develops by suppression of decapacitation
factors. It occurs by following processes.
1) Dilution of inhibitory factors present in semen.2) Washing of cholesterol vesicles covering the sperm
head.
3) Removal of membrane cholesterol of the acrosome. This
weakens the sperm covering.
4) Entering of Ca2+ into the sperm. This changes the
movement of sperm tail from slower undulating motion
to fast whiplash motion.
Physical and chemical events involved in fertilization:
a)Acrosome reaction: secondary oocyte reaching the
oviduct is covered by zona pellucida and corona radiata.
A capacitated sperm enters the corona radiata to reach
the zona pellucida. One of three glycoproteins (ZP1,
ZP2, ZP3) ZP3 functions as sperm receptor and binds
with the complementary molecule on the sperm head. It
induces the sperm to release its hydrolytic enzymes
collectively called as sperm lysins.
These sperm lysins are as:
i) Hyaluranidase: this is the enzyme which
hydrolyses the hyaluronic acid of follicular cells. It
also dissolves the cementing material between the
follicular cells leading their separation.
ii) corona penetrating enzyme: This is the enzyme
which dissolves the corona radiata layer around the
oocyte by hydrolyzing their ground substances.iii) Acrosin or zona lysin: This is the enzyme which
helps in the digestion of zona pellucida. This process
is also called as compatibility reaction. By this
reaction there is also the formation of an outgrowth
called as fertilization cone. It occurs by the special
proteins present on the zona pellucida and sperm
surface. These proteins are termed as fertilizin and
anti-fertilizin.
Optimum PH, Ca2+ and Mg 2+ concentration is also
important for the acrosomal reaction.
b)Cortical reaction: Soon after the fusion of sperm and egg
membranes egg shows the cortical reaction to prevent
entry of more than one sperms. Due to the contact
between sperm head and fertilization cone, Ca 2+ wave is
initiated which causes extrusion of cortical granules out
of the egg. They bring about the modification of plasma
membrane and change it into fertilization membrane or
activation calyx. It does not allow the other sperms to
enter the egg.
Cortical granules actually release their enzymes
between plasma membrane of oocyte and zona
pellucida. These harden the zona pellucida to become
a barrier for other sperms.
c) Sperm entry: as discussed earlier ovum extends finger
like microvilli around the entering sperm to form fertilization cone. Sperms thus enter the egg. Distal
centriole splits into two centrioles to generate mitotic
spindles for cell division.
d) Karyogamy/Amphimixis : Sperm entry stimulates the
egg to resume and complete the suspended meiosis II.
This produces a mature haploid ovum and a secondary
polar body. At this time sperm head separates from
middle piece and tail, and becomes the male pronucleus.
Polar body and tail sooner degenerate. Chromosomes
od egg are not organized into a nucleus. They represent
female pronucleus. Chromosomes of sperm are set free
by breaking down the nuclear envelope. Two sets of
chromosomes go over a spindle formed between the
centrioles. Mixing up of chromosome sets of ovum and
sperm is called as Amphimixis or Karyogamy. This
completes the process of fertilization. It combines the
genetic information from two parents. Ovum is now a
diploid cell termed as zygote. Mother is now said to be
pregnant.
Early embryo development or embryogenesis is the
development of embryo fertilized ovum and its subsequent
development into young organism. It has three major stages;
cleavage, gastrulation and organogenesis.
Cleavage: It is a series of mitotic divisions of zygote
following fertilization forming a blastula.
Difference between cleavage and ordinary mitosis: The
cleavage is basically mitosis producing diploid cells. They
differ from typical mitosis in a few points:
1)Divisions occur in quick succession.
2)Interphase in cleavage is short and does not
involve growth so that the resulting blastomeres
become smaller in size and their number
increases.
3) DNA synthesis occurs faster in cleavage to
facilitate the duplication of chromosomes for the
rapidly forming new blastomeres.
4)Shape of embryo does not change during cleavage
because there is no movement of blastomeres.
5)Oxygen consumption generally increases during
cleavage to provide adequate energy for activities
taking place in rapid cell division.
In nutshell
during cleavage,
the cell
undergoes
mitosis and
synthesis phase
of cell cycle but
they skip growth
phases.
Cleavage in human zygote: It occurs during the passage of
zygote through the oviducts to the uterus. It is holoblastic i.e.
it divides zygote and blastomeres completely into daughter
cells. However blastomeres differ in size from the start. This
number does not increase by simply doubling the sequence
as occurs in frog. First cleavage occurs about 30 hours after
fertilization. It occurs along animal-vegetal pole axis. It
produces two blastomeres, one slightly larger than the other.The two blastomeres remain adhered to one another. The
second cleavage occurs within 60 hours after fertilization. It
is at the right angle to the plane of first division and divides
each blastomere into two. The larger blastomere divides a
little bit sooner as compared to smaller one so there is an
intermediate 3-cell stage before the characteristic 4-cell
stage. Third
cleavage occurs
72 hours after
fertilization.
Morula
stage: Cleavage
division
produces a ball
of cells called as
morula. It has 8-
16 cells,
occasionally 32
cells may also be
present. It is still
covered by zona pellucida. It undergoes compaction. It
actually means tightly adhering of blastomeres due to the
formation of proteins called as cohesions.
Outer peripheral cells are flatter, smaller and with tight
junctions. Inner cell mass contains slightly larger roundedcells with gap junctions. Morula does not remain in the
ampulla part of oviduct but slowly descends towards the
uterus in 4-6 days. The descent is caused due to the feeble
fluid current produced by secretory and ciliary activity
mucoidal epithelium. During this period corona radiata
detaches.
Significance of Cleavage:
i) It converts unicellular zygote into a multicellular
embryo.
ii) It is rapid cell division and daughter cells do not need
to grow before the next division.
iii) There occurs reduction in cell size.
iv) Non development of cell junctions is seen which helps
in rearrangement of cells.
Formation of Blastula: outer layer of cells of morula now
absorbs the nutritive fluid secreted by the uterine mucus
membrane (also called as
uterine milk), enlarge and
flatten further to form
trophoblast or
trophoectoderm.
Trophoblast secretes
a fluid into the interior
creating a cavity called as Blastocoel. But it is to be noted here that according to
various publications this fluid is not secreted by trophoblast
cells rather it is absorbed from uterine secretions by
trophoblast cells.
As the quantity of fluid increases, the morula enlarges
rapidly and assumes the size of a cyst. It is then called as
Blastocyst.
Now, inner cell mass looks like a knob at one pole. The
knob gives rise to the embryo hence called as embryonal
knob. The side of the blastocyst to which embryonal knob is
attached is called as embryonic pole or animal pole. The
trophoblast does not take part in formation of embryo
proper. It remains external to the embryo and gives rise to
extra embryonic membranes viz chorion, allantois, yolk sac
and amnion for the protection and nourishment of embryo.
Trophoblast cells in direct contact with embryonal knob are
called as cells of rauber.Implantation: Blastocyst contains outer trophoblast
and inner cell mass. Inner cell mass gives rise to the embryo
while as trophoblast gives rise to the extra embryonic
membranes viz chorion, amnion, allantois and yolk sac.
During implantation blastocyst is attached to and buried into
endometrium of uterus. But it should not be implanted on
wrong site. Wrong implantation is prevented by zona
pellucida.While moving through the oviduct towards uterus,
blastocyst expands within zona pellucida. Trophoblast cell
membranes contain Na+/K+-ATPase also called as sodium-
potassium pump facing the blastocoel. These ATPase
complexes pump Na+ ions into blastocoel which in turn
causes osmosis of water into blastocoel cavity, thus
enlarging blastocoel. During this time zona pellucida
prevents the attachment of blastocyst to oviduct walls. If
blastocyst is attached to the oviduct walls, it will cause tubal
pregnancy or ectopic pregnancy. It is a dangerous condition
which may cause life threatening hemorrhage.
Mammalian blastocyst hatches from the zona pellucida
by lysing a small hole as the blastocyst expands. Once out the
blastocyst can make direct attachment to the uterus.
Sometimes during the process while a blastocyst is coming
out of zona layer it may break into two blastocysts which
causes the formation of monozygotic (identical) twins. Pregnancy and embryonic development:
Pregnancy is a
condition of having developing embryo or foetus inside the womb of the
mother. Soon after the implantation, the surface cells of the
trophoblast secrete lytic enzymes which cause erosion of
endometrium. They also give rise to outgrowths called as
chorionic villi. Chorionic walls and uterine walls become
interdigitated. The villi not only help in attachment but also
in absorbtion of nutrients.
Uterine tissue undergoes nutrient enrichment, enlargement
and formation of uterine part of placenta called as decidua.
Decidua has three regions viz decidua basalis, decidua
peritalis, and decidua capsularis.
Trophoblast covering secretes a hormone called as
Human Chorionic Gonadotropin (HCG). Hormone can be
detected in urine of gravid woman within a day or so after
implantation.It helps in secretion of progesterone inorder to
prevent menstruation. Progesterone induces the cervical
glands to secrete viscous mucus for filling the cervical canal
to form a protective plug. Therefore progesterone is also
termed as pregnancy hormone.
Gastrulation:
During blastocyst formation there was the formation of
embryonal knob which soon shows rearrangement to form
an embryonic disc also called as bilaminar disc.During gastrulation, movement of cells occurs in small
masses or sheets so as to
form primary germ layers.
There are three germ layers
in mammalian embryo viz
ectoderm, mesoderm and
endoderm. These cell
movements are also called as
morphogenetic movements.
Production of gastrulation is a
ball of cells called as gastrula
which is different from
blastocyst in various characteristics.
Formation of primary germ layers:
inner cell mass or embryonal knob possesses the stem cells
which have a tendency to form all types of tissues and
organs. Normally they get rearranged to form a flat disc
called as embryonic disc or germinal disc. It differentiates
into two layers outer epiblast of larger columnar cells and
inner smaller cuboidal hypolast. Hypoblast functions as
embryonic endoderm. It is the first germinal layer to
differentiate.Hypoblast grows on the sides and forms a covering over the
blastocoel. This converts the blastocoel into primary yolk
sac. Meanwhile trophoblast of the region grows to form
extra embryonic mesoderm.it splits up and forms extra
embryonic coelom.it compresses the primary yolk sac.
Secondary smaller yolk sac is thus formed. Simultaneously
embryonic endoderm forms a tube of its own. This is the gut
of the embryo.
Most of the epiblast grows laterally to produce
ectoderm. However at one point epilast cells proliferate to
form a first cellular elevation called primitive streak. Cells of
primitive streak continue to proliferate and pass out in
between epilast and hypoblast forming third germ layer
called as mesoderm.
Formation of
extra embryonic
membranes:
Need for foetal
membranes:
Embryo of an aquatic organism is surrounded by water,
which protects
the embryo, keeps
it moist, removes
waste and
permits gaseous
exchange. In
terrestrial
vertebrates these
all functions are
taken up by
embryonic
membranes, some of which take part in the formation of
placenta in
mammals. The
placenta
develops
before emryo
and because
embryo
depends upon
it.Four
extra embryonic membranes are as:
1)Yolk sac
2)Amnion
3)Chorion
4)Allantois
Yolk sac: It is formed below the embryo. It contains fluid
but not yolk. Yolk sac is vestigial organ inherited from avian
ancestors. We have almost discussed how primary and
secondary yolk sacs were formed. Yolk sac becomes the site
of blood cell formation until the function is taken up by liver
at about 6th week of gestation. Therefore yolk sac begins to
shrink.
Amnion: It is formed above the embryo. It consists of
trophoblast and mesoderm. It encloses a fluid filled space
called as amniotic cavity. Amnion and amniotic cavity
enlarge and hence cover the entire embryo. Embryo is
suspended in amniotic cavity by an umbilical cord. Umbilical
cord is forms of stalks of yolk sac and allantois. The main
blood vessels from placenta reach the foetus through
umbilical cord.
According to some authors actual origin of amniotic
fluid is not properly known however it can be of dual origin
i.e. foetal as well as maternal. Some authors believe that it is
derived from foetal kidneys and urinary bladder. In much
simpler terms amniotic fluid is derived from foetal urine. It
is completely replaced every 24 hours.
Functions of amniotic fluid:
1)It cushions the embryo protecting it from mechanical
shocks, injuries and stress because of maternal organs.
2)It permits foetal movement.
3)It prevents bacterial infections.
4)It maintains a constant pressure and temperature.
Allantois: It is a small membranous sac that is pushed out
from the gut. It remains small and does not reach chorion. It
forms the arteries and veins to vascularize the chorion. It
also forms the blood cells. Due to presence of allantois
human placenta is called as Allantochorionic.
Chorion: it is the outer most foetal membrane and
surrounds the foetus completely. It is covered by mesoderm
and trophoblast. It protects the embryo and forms the
placenta for metabolic exchange between foetus and mother.
Human placenta:
It is a foeto-maternal connective that develops during
pregnancy and forms a temporary association between
maternal and foetal tissues for supporting the foetus during
its development. Foetus is connected with the placenta by a
long flexible string called as umbilical cord. It is mainly
formed of allantois and is covered by amniotic epithelium.
Cord contains two arteries and a single vein. Arteries
transport deoxygenated blood from foetus while as veintransports oxygenated blood to the foetus. Human placenta
is deciduate which means that it is passed out at the time of
parturition. Though the placenta is first developed all
around the embryo but later on it remains restricted into a
disc shaped area, so it is called as metadiscoidal placenta. It
is also called as chorionic placenta because it is mainly
derived from chorion. It also contains few parts derived
from allantois. Decidua basalis contains some blood sinuses
into which the blood vessels of chorionic villi are immersed.
In the region of contact, the epithelium, connective tissue
and endothelial linings are corroded. Only the foetal barriers
present over the blood vessels persist. Such a placenta is
called as haemochorial placenta.
Functions of placenta:
1)Foetus receives all the nutrients from maternal blood
via placenta. The transfer occurs through the diffusion
and active transport.
2)Placenta helps in the exchange of respiratory gases.
3)Placenta stores fat and glycogen which can e broken
down and absorbed by foetus.
4)Foetus excretes its toxic wastes through placenta.
5)Maternal antibodies enter the foetus through placenta
which protects foetus from various diseases and
disorders.
6)Placenta does not allow any pathogen or toxic materials
to enter the foetal circulatory system.
7) Placenta is an important endocrine gland that produces
a number of hormones, which are discussed as follows:
i) Human Chorionic Gonadotropin: its secretion starts
immediately after the implantation. The hormone
acts upon corpus decidua just as LH, causes it to
grow and maintain it for long term pregnancy. They
prevent menstruation, stimulate the endometrium to
grow and store nutrients, and cervix to plug the
passage by viscous secretions. It also acts on male
foetus’s testes, stimulating the secretions of
testosterone and development of male sex organs.
ii) Chorionic thyrotrophin: it stimulates mothers thyroid
gland for producing more hormones.
iii) Chorionic corticotrophin: it acts on adrenal glands of
mother to stimulate the secretion of hormones.
Increased secretion of aldosterone helps the mother
to retain sodium hence more fluid in the body. It
occasionally leads to the pregnancy hypertension in
the mother.
Placenta may also secrete corticotrophin
releasing hormone (CRH) which may
determine the timing of parturition as excess
of it has been found to cause prematuredelivery while as its lower level delays the
child birth.
iv) Human Placental lactogen: The hormone functions as
weak growth hormone. It stimulates growth of
breasts. It decreases insulin sensitivity of mother so
that the mother in unable to utilize more glucose.
Hence the glucose become s available for foetus.
v) Progestogens: progestogen helps in maintaining
pregnancy, decreasing contractility of uterus, growth
of endometrium etc. It is because of its importance in
maintaining pregnancy that it is called as pregnancy
hormone.
vi) Estrogen: placenta converts adrenal androgen of
mother and foetus into the estrogen. The hormone
help in enlargement of pregnant uterus, enlargement
and growth of breasts, growth of mothers external
genitalia besides relaxing pelvic ligaments.
vii) Relaxin: it is secreted both y corpus luteum and
placenta. The hormone softens the connective tissue
of symphisis pubica for reducing discomfort of
carriage, and facilitating easy child birth. It also
dilates cervix and loosenes the ligaments of
- sacroiliac and sacrococcygeal joints.
Organogenesis: organogenesis can be defined as
formation of tissues and organs in the embryo. It begins with the third week of pregnancy. Most of the organogenesis is
completed within one month. First sign of organogenesis is
notogenesis, followed by neurulation or appearance of
rudiments of nervous system. It starts with the development
of a fold of ectoderm called as neural plate. Neural plate is
premodium of nervous system. Soon the rudiments of other
organs also begin to appear. With the beginning of
organogenesis embryo is converted into foetus.
After the first month of pregnancy, heart of the foetus is
developed. Heartbeat of the foetus can be heard by the
stethoscope. Limbs and digits develop by the end of second
of second month. By the end of 12 weeks i.e. first trimester
most of the major organ systems develop including external
genitalia.
During the first trimester of pregnancy, the foetus is
sensitive to various antibiotics, drugs, pathogens, and toxic
chemicals they can cause malformations in foetus so they are
called as teratogens. Fourth month of pregnancy is
characterized by the fast development of foetus. There are
minor alterations of the structure. Teratogen effect is very
minimum.
During fifth month hairs appear on head and foetus
begins to change positions. These movements are also called
as foetal movements and continue till parturition. After 24
weeks ie second trimester body is covered with fine hairs.Eye lids separate and eye lashes develop. Foetus is fully
developed after 9 months. So after 9 months parturition
occurs.
Parturition:
Parturition is the process of giving birth to the baby. The
physical events involved in the parturition like uterine and
abdominal contractions, dilation of cervix, and passage of
baby are collectively called as labour. Labour is accompanied
by localized sensation of discomfort called as labour pain.
Parturition is controlled by complex neuroendocrine
mechanism. Signals originate from fully developed foetus
and placenta. They cause mild uterine contractions called
foetal ejection reflex. It is accompanied by rise in estrogen to
progesterone ratio, increase in oxytocin receptors in uterine
muscles, increase in the oxytocin secretion by mother and to
a less extent by foetus followed by stretching of uterine
muscles.
1)Dilation stage:-Uterine contractions begin from top.
They occur once in every thirty minutes. Contractions
force the baby towards cervix. The intervals between
successive contractions decrease to about every 1-3
minutes. Contractions are accompanied by pain caused
compression of blood vessels and subsequent hypoxia
of uterine muscles. Contractions are under positive
feedback. Oxytocin induces uterine contractions which prolactin, while as release of milk is controlled by the
hormone oxytocin within 30-60 seconds after the baby
starts sucking.
Breasts: These are rounded eminences located over
the pectoral muscles on the front wall of thorax. These
enlarge considerably in adult female. Each breast has a
nipple surrounded by a circular, pigmented area called
areola. The breasts contain fatty and connective tissues.
Moreover they contain mammary glands also. Mammary
glands are compound saccular nipples of lactiferous ducts.
Just under the nipples, lactiferous ducts widen to form
lactiferous sinuses to store milk. A nursing mother produces
about 1-2 liters of milk a day.
Sexually transmitted diseases or venereal diseases are
reproductive tract infections transmitted from one human
being to another by copulation e.g. Gonorrhea, Syphilis,
chlamydia, Trichomoniasis, genital warts, genital herpes,
HIV-AIDS etc. except genital herpes, HIV-AIDS, and hepatitis
B, all other STDs are curable provided that they should be
detected earlier. Early symptoms are generally minor like
itching, fluid discharges, mild pain, and swelling in genital
regions. They may even be asymptomatic (with no
prominent symptoms) especially in case of females so
remain undetected for long. Moreover due to the hesitation
and social stigma people infected with STDs do not usually
visit the doctors for treatment.Uncured STDs cause pelvic inflammatory diseases,
abortion, still birth (death of the foetus between 24th week of
gestation and parturition), ectopic or tubal pregnancy,
infertility and reproductive tract cancer. It is necessary to
note here that incidence of STDs is high in age groups 15-24
years. STDs can be prevented by; use of condoms, and
avoiding multi-partner and homosexual relationships.
Some Sexually transmitted diseases and their treatment are
discussed as follows:
Chlamydia: It is sexually transmitted disease caused due
to a bacteria Chlamydia trachomatis. This infection can also
cause trachoma, an infectious disease which makes inner
eyelids rough, leads to pain in eyes, breaking of cornea, and
even blindness. Chlamydia is obligate intracellular parasite
which passes through two stages viz reticular body stage
and elementary body stage. Infection causes urethritis
(Inflammation of urethra), epididymitis (inflammation of
epididymis), yellow mucus and pus, rectal pain and
development of granulomatous masses.
Treatment: usually there are a group of antibiotics
prescribed by doctors e.g. Tetracycline, Erythromycin,
doxycycline, and azithromycin.
Gonorrhea: it is a sexually transmitted disease also called
as clap or drip.Diagnosis of Gonorrhea went up by 15% in England
between 2012 and 2013 with a large number of these cases
being among homosexual men.
It is caused by Neisseria gonorrheae a bacterium which can
easily develop in mucus membrane of the body. It can live in
the warm and moist areas of reproductive organs including
cervix, oviducts, urethra, urinary bladder and also in mouth,
throat and anus.
Symptoms: the bacterium passes into the genital tubes, form
pus containing discharge, pain over genitalia and burning
while urination. It may also cause arthritis and eye diseases.
Eyes of babies born of infected mothers are damaged.
Other symptoms may include greenish, yellow or whitish
discharge from vagina, Lower abdominal or pelvic pain,
conjunctivitis (red itchy eyes), bleeding between periods,
spotting (bleeding) after intercourse, swelling of vulva,
burning in throat and swollen glands in throat.
Treatment: penicillin and ampicillin are effective drugs in
gonorrhea, but drug resistance have been found for
penicillin.
Trichomoniasis: This sexually transmitted disease is
caused by a tetra flagellate protozoan parasite called as
Trichomonas vaginalis producing mechanical stress on the
host cells, and then ingesting the cell fragments. It isprimarily an infection of urinogenital tract. Most common
sites of infection are urethra and vagina in women.
In women it causes foul smelling vaginitis with
yellowish discharge, vulvar erythema (redness of skin or
mucous), and burning dysuria.
In males it causes urethritis, epididymitis, prostatitis, and
burning dysuria.
Treatment of both pregnant and non-pregnant women
includes metronidazole up to 2000mg (2g). caution should
be used in pregnant women.
Genital warts: This disease is caused by Human Papilloma
Virus. It is characterized by warts on skin of genital areas.
These warts are smaller and can be aggregated. In women
warts may enter the vagina and cervix.
Treatment includes podofilox which is applied twice daily
morning and evening for three consecutive days followed by
withhold for four days. This cycle may be repeated up to four
times unless the warts disappear. If warts persist, then the
doctor must be consulted.
Imiquimod is a prescribed medication that acts as
immune response promoter drug and is used to cure warts.
It is applied in the form of cream. It can also be used in
superficial basal cell carcinoma. In case of organ transplant
Imiquimod should not be taken.If Imiquimod as well as podofilox are not helpful, then
warts are removed by surgical method.
Genital herpes: this is a sexually transmitted disease
caused by Herpes simplex virus. There are vasiculopustular
lesion and clusters of reddish ulcers over external genitalia
and perianal areas, swelling of inguinal lymph nodes, pain,
urethral and vaginal discharges, dysuria, headache and
malaise.
Treatment: Acyclovir, Velacyclovir and famciclovir should be
taken in the form of powder, tablet, solution or suspension.
Conchoids: This disease is caused by bacterium
Haemophilus ducrey. Painful bleeding ulcers develop on the
external genitalia accompanied by swelling of nearby lymph
nodes. Drugs used include erythromycin, ciprofloxacin, and
ceftriaxone.
Syphilis: It is the disease caused by Treponema palladium.
An indurated, infectious but painless primary ulcer develops
on the genitals. Lymph nodes swell up,. Soon the primary
ulcer heals up, skin lesions, swollen joints and flu-like
conditions appear with loss of hairs in secondary stage.
Tertiary stage is characterized by chronic ulcers on nose,
lower leg and palate.
Treatment includes penicillin and tetracyclin.
Birth control........Needs and Methods
It is the regulation of conception by preventive methods or
devices to limit the number of children. The birth control
methods which deliberately prevent fertilization are reffered
to as contraception. Contraception amy be temporary or
permanent.
Need for birth control: in 1900 AD words population
was less than 2 billion. It was increased to 6 billion in 2000
AD. Population of India was 238 million in 1901. It became
350 million in 1947, 1000 million in May 2000 AD and 1.21
billion in 2011. While world population rose by slightly
more than thrice, Indian population grew by nearly five
times during 20th century. Today India accounts for 17.5 %
of total world’s population with only 2.4 % of land area. The
tremendous increase in size and growth of population is
called as population explosion. This population explosion
creates the need to control the further rapid increase in the
population. Thus it is necessary to promote family welfare
programs and contraception.
Birth control methods
Contraceptives: they are the devices which prevent
conception or pregnancy without interfering with the
reproductive health of the individuals.Ideal contraceptive should be: User friendly, without any
side effect, reversible, completely effective against
pregnancy.
Contraception methods include natural, barrier, oral,
IUDs, injectable, implants, and surgical methods. According
to survey there were 60.79 lakh IUD insertions, 48.74 lakh
sterilizations, 249.9 lakh condom users and 87.54 lakh oral
pill users in 2004.
Contraceptive methods are categorized into following main
categories
1)Natural method: these are the methods of contraception
which do not require any device, medicine or surgery.
These methods include safe period (periodic
abstinence), coitus interruptus, and lactational
amenorrhea.
i) Safe period/ periodic abstinence: it is also called as
rhythm method because it involves refraining from
sexual intercourse when chances of fertilization are
higher. Ovulation roughly occurs in the middle of
menstruation i.e. about 13th or 15th day of menstrual
cycle. Fertility period is up to 48 hours after
ovulation. Preventing sex during fertility period can
prevent conception. Ovulation period can be
diagnosed as the temperature of the body dips to below average and then rises by about 1oF,
remaining there for the rest of the cycle.
During fertility period cervical mucus is slippery
and can be drawn into a thread when stretched
between two fingers. Another test called as I-sure is
also available in market to know the fertility period.
Period prior to ovulation is safe for copulation.
period after 4th day of temperature rise is also safe.
It is always better to avoid sex from day 10 to day 17
of the menstrual cycle. This method is called as
periodic abstinence.
ii) Withdrawal method/ coitus interreptus: this is the old
method of birth control which was in use about 2000
years ago. It involves the withdrawal of penis from
the female urinogenital tract before ejaculation so
that sperms are not deposited in the female’s vagina.
This method does not work always as there may be
delay in withdrawal of penis.
iii) Lactation amoenorrhoea : just after the parturition
there is the phase of absence of menstruation or
amoenorrhoea. It is actually the phase of intense
lactation. Breast feeding the child prevents
conception. But this method works hardly up to six
months.2)Barrier method: these are the mechanical devices
which prevent the deposition of sperms in the vagina
and their passage to uterus, hence prevent the
fertilization. Further they can be inserted by the user in
complete privacy without any help of a medical
practitioner or surgeon. Common barriers are condoms,
diaphragms, fem shield and cervical cap.
i) Condom: This is a thin sheath usually made up of
rubber to cover the penis. It also prevents people
from spreading STDs.
ii) Diaphragm: it is tubular sheath with a flexible
metal or a spring ring which is fitted in vagina.
iii) Fem sheath: the device is polyurethane pouch
with rings at either side. Inner ring is smaller and
present on inner closed side. It is used as female
condom.
iv) Cervical cap and vault cap : cervical cap is a
rubber nipple which is fitted over cervix and is
designed to remain there by suction. On the other
hand vault cap is a hemisphere dome like rubber or
plastic cap with a thick rim meant for fitting over
cervix.
3)Chemical methods: These are the contraceptives which
contain spermicide chemicals. Chemical contraceptives
are in the form of creams, foam, tablets, gel etc. They
commonly contain lactic acid, Boric acid, citric acid, zinc sulphate and potassium permanganate. These
contraceptives are introduced into vagina, prior to
copulation
Sponge is now a foam suppository or tablet containing
Non-oxynol-9 as spermicide. It is moistened before use to
activate spermicide. The device also absorbs ejaculate.
4)Intra-uterine devices: They are the devices made up of
plastic, metal or both which are inserted into female’s
uterus to prevent conception. These may be loops,
spirals, rings, bowls, shields, or T’s. IUDs are generally
categorized into three main classes viz Inert IUDs,
Copper releasing IUDs, and hormone releasing IUDs.
These devices generally contain spermicides and
chemicals capable of killing a sperm.
5)Oral contraceptives: they are the contraceptive
preparations containing progestin either alone or with
combination of oestrogen. Pills are taken orally for 21
days in a menstrual cycle starting from day 5 to day 25,
and then it is restarted after 7 days for next phase.
These act mainly by four ways: a) inhibition of
ovulation, b) alternation of endometrium so as to make
it unsuitable for implantation, c) change in the cervical
mucus so as to prevent passage of sperms through
cervix, d) inhibition of motility and secretion phase of
fallopian tubes. Examples of oral pills are Mala D, Mala L
etc.6)Injectable contraceptives: Two types of injectable
contraceptive preparations are used usually viz depot-
medroxy progesterone acetate(150mg/300mg), or
norethisterone enanthate (200mg).
7)Implants: they are hormone containing devices which
are implanted sub-dermally for long term
contraception. Norplant is an implant device with six
small permeable capsules which are implanted in the
skin in the fan-shaped manner. These contain progestin
which is slowly diffused into tissues and help in
contraception. These works for about 5 years.
8)Surgical methods: these are the permanent methods of
contraception. Methods are operative procedures which
block the passage of semen in males and ova in females.
Techniques are called as sterilization methods. These
include vasectomy and tubectomy. Vasectomy is the
procedure in which vasa deferentia is cut and occluded
so as to block the passage of sperms. On the other hand
in tubectomy oviducts are cut and ligated.
Medical termination of pregnancy: it is the
deliberate abortion of child in which pregnancy is
damaged before the full term of gestation period.
Almost 20% of total world pregnancies are aborted.
Number of medical termination of pregnancy is about
40-50 million per year. In India there is a law and a
proper act has been developed regarding the MTP,Medical Termination of Pregnancy act 1971. These are
usually performed after amniocentesis and Sonography,
in conditions like rape, unwanted pregnancy, and
malformed children.
formation of tissues and organs in the embryo. It begins with the third week of pregnancy. Most of the organogenesis is
completed within one month. First sign of organogenesis is
notogenesis, followed by neurulation or appearance of
rudiments of nervous system. It starts with the development
of a fold of ectoderm called as neural plate. Neural plate is
premodium of nervous system. Soon the rudiments of other
organs also begin to appear. With the beginning of
organogenesis embryo is converted into foetus.
After the first month of pregnancy, heart of the foetus is
developed. Heartbeat of the foetus can be heard by the
stethoscope. Limbs and digits develop by the end of second
of second month. By the end of 12 weeks i.e. first trimester
most of the major organ systems develop including external
genitalia.
During the first trimester of pregnancy, the foetus is
sensitive to various antibiotics, drugs, pathogens, and toxic
chemicals they can cause malformations in foetus so they are
called as teratogens. Fourth month of pregnancy is
characterized by the fast development of foetus. There are
minor alterations of the structure. Teratogen effect is very
minimum.
During fifth month hairs appear on head and foetus
begins to change positions. These movements are also called
as foetal movements and continue till parturition. After 24
weeks ie second trimester body is covered with fine hairs.Eye lids separate and eye lashes develop. Foetus is fully
developed after 9 months. So after 9 months parturition
occurs.
Parturition:
Parturition is the process of giving birth to the baby. The
physical events involved in the parturition like uterine and
abdominal contractions, dilation of cervix, and passage of
baby are collectively called as labour. Labour is accompanied
by localized sensation of discomfort called as labour pain.
Parturition is controlled by complex neuroendocrine
mechanism. Signals originate from fully developed foetus
and placenta. They cause mild uterine contractions called
foetal ejection reflex. It is accompanied by rise in estrogen to
progesterone ratio, increase in oxytocin receptors in uterine
muscles, increase in the oxytocin secretion by mother and to
a less extent by foetus followed by stretching of uterine
muscles.
1)Dilation stage:-Uterine contractions begin from top.
They occur once in every thirty minutes. Contractions
force the baby towards cervix. The intervals between
successive contractions decrease to about every 1-3
minutes. Contractions are accompanied by pain caused
compression of blood vessels and subsequent hypoxia
of uterine muscles. Contractions are under positive
feedback. Oxytocin induces uterine contractions which prolactin, while as release of milk is controlled by the
hormone oxytocin within 30-60 seconds after the baby
starts sucking.
Breasts: These are rounded eminences located over
the pectoral muscles on the front wall of thorax. These
enlarge considerably in adult female. Each breast has a
nipple surrounded by a circular, pigmented area called
areola. The breasts contain fatty and connective tissues.
Moreover they contain mammary glands also. Mammary
glands are compound saccular nipples of lactiferous ducts.
Just under the nipples, lactiferous ducts widen to form
lactiferous sinuses to store milk. A nursing mother produces
about 1-2 liters of milk a day.
Sexually transmitted diseases or venereal diseases are
reproductive tract infections transmitted from one human
being to another by copulation e.g. Gonorrhea, Syphilis,
chlamydia, Trichomoniasis, genital warts, genital herpes,
HIV-AIDS etc. except genital herpes, HIV-AIDS, and hepatitis
B, all other STDs are curable provided that they should be
detected earlier. Early symptoms are generally minor like
itching, fluid discharges, mild pain, and swelling in genital
regions. They may even be asymptomatic (with no
prominent symptoms) especially in case of females so
remain undetected for long. Moreover due to the hesitation
and social stigma people infected with STDs do not usually
visit the doctors for treatment.Uncured STDs cause pelvic inflammatory diseases,
abortion, still birth (death of the foetus between 24th week of
gestation and parturition), ectopic or tubal pregnancy,
infertility and reproductive tract cancer. It is necessary to
note here that incidence of STDs is high in age groups 15-24
years. STDs can be prevented by; use of condoms, and
avoiding multi-partner and homosexual relationships.
Some Sexually transmitted diseases and their treatment are
discussed as follows:
Chlamydia: It is sexually transmitted disease caused due
to a bacteria Chlamydia trachomatis. This infection can also
cause trachoma, an infectious disease which makes inner
eyelids rough, leads to pain in eyes, breaking of cornea, and
even blindness. Chlamydia is obligate intracellular parasite
which passes through two stages viz reticular body stage
and elementary body stage. Infection causes urethritis
(Inflammation of urethra), epididymitis (inflammation of
epididymis), yellow mucus and pus, rectal pain and
development of granulomatous masses.
Treatment: usually there are a group of antibiotics
prescribed by doctors e.g. Tetracycline, Erythromycin,
doxycycline, and azithromycin.
Gonorrhea: it is a sexually transmitted disease also called
as clap or drip.Diagnosis of Gonorrhea went up by 15% in England
between 2012 and 2013 with a large number of these cases
being among homosexual men.
It is caused by Neisseria gonorrheae a bacterium which can
easily develop in mucus membrane of the body. It can live in
the warm and moist areas of reproductive organs including
cervix, oviducts, urethra, urinary bladder and also in mouth,
throat and anus.
Symptoms: the bacterium passes into the genital tubes, form
pus containing discharge, pain over genitalia and burning
while urination. It may also cause arthritis and eye diseases.
Eyes of babies born of infected mothers are damaged.
Other symptoms may include greenish, yellow or whitish
discharge from vagina, Lower abdominal or pelvic pain,
conjunctivitis (red itchy eyes), bleeding between periods,
spotting (bleeding) after intercourse, swelling of vulva,
burning in throat and swollen glands in throat.
Treatment: penicillin and ampicillin are effective drugs in
gonorrhea, but drug resistance have been found for
penicillin.
Trichomoniasis: This sexually transmitted disease is
caused by a tetra flagellate protozoan parasite called as
Trichomonas vaginalis producing mechanical stress on the
host cells, and then ingesting the cell fragments. It isprimarily an infection of urinogenital tract. Most common
sites of infection are urethra and vagina in women.
In women it causes foul smelling vaginitis with
yellowish discharge, vulvar erythema (redness of skin or
mucous), and burning dysuria.
In males it causes urethritis, epididymitis, prostatitis, and
burning dysuria.
Treatment of both pregnant and non-pregnant women
includes metronidazole up to 2000mg (2g). caution should
be used in pregnant women.
Genital warts: This disease is caused by Human Papilloma
Virus. It is characterized by warts on skin of genital areas.
These warts are smaller and can be aggregated. In women
warts may enter the vagina and cervix.
Treatment includes podofilox which is applied twice daily
morning and evening for three consecutive days followed by
withhold for four days. This cycle may be repeated up to four
times unless the warts disappear. If warts persist, then the
doctor must be consulted.
Imiquimod is a prescribed medication that acts as
immune response promoter drug and is used to cure warts.
It is applied in the form of cream. It can also be used in
superficial basal cell carcinoma. In case of organ transplant
Imiquimod should not be taken.If Imiquimod as well as podofilox are not helpful, then
warts are removed by surgical method.
Genital herpes: this is a sexually transmitted disease
caused by Herpes simplex virus. There are vasiculopustular
lesion and clusters of reddish ulcers over external genitalia
and perianal areas, swelling of inguinal lymph nodes, pain,
urethral and vaginal discharges, dysuria, headache and
malaise.
Treatment: Acyclovir, Velacyclovir and famciclovir should be
taken in the form of powder, tablet, solution or suspension.
Conchoids: This disease is caused by bacterium
Haemophilus ducrey. Painful bleeding ulcers develop on the
external genitalia accompanied by swelling of nearby lymph
nodes. Drugs used include erythromycin, ciprofloxacin, and
ceftriaxone.
Syphilis: It is the disease caused by Treponema palladium.
An indurated, infectious but painless primary ulcer develops
on the genitals. Lymph nodes swell up,. Soon the primary
ulcer heals up, skin lesions, swollen joints and flu-like
conditions appear with loss of hairs in secondary stage.
Tertiary stage is characterized by chronic ulcers on nose,
lower leg and palate.
Treatment includes penicillin and tetracyclin.
Birth control........Needs and Methods
It is the regulation of conception by preventive methods or
devices to limit the number of children. The birth control
methods which deliberately prevent fertilization are reffered
to as contraception. Contraception amy be temporary or
permanent.
Need for birth control: in 1900 AD words population
was less than 2 billion. It was increased to 6 billion in 2000
AD. Population of India was 238 million in 1901. It became
350 million in 1947, 1000 million in May 2000 AD and 1.21
billion in 2011. While world population rose by slightly
more than thrice, Indian population grew by nearly five
times during 20th century. Today India accounts for 17.5 %
of total world’s population with only 2.4 % of land area. The
tremendous increase in size and growth of population is
called as population explosion. This population explosion
creates the need to control the further rapid increase in the
population. Thus it is necessary to promote family welfare
programs and contraception.
Birth control methods
Contraceptives: they are the devices which prevent
conception or pregnancy without interfering with the
reproductive health of the individuals.Ideal contraceptive should be: User friendly, without any
side effect, reversible, completely effective against
pregnancy.
Contraception methods include natural, barrier, oral,
IUDs, injectable, implants, and surgical methods. According
to survey there were 60.79 lakh IUD insertions, 48.74 lakh
sterilizations, 249.9 lakh condom users and 87.54 lakh oral
pill users in 2004.
Contraceptive methods are categorized into following main
categories
1)Natural method: these are the methods of contraception
which do not require any device, medicine or surgery.
These methods include safe period (periodic
abstinence), coitus interruptus, and lactational
amenorrhea.
i) Safe period/ periodic abstinence: it is also called as
rhythm method because it involves refraining from
sexual intercourse when chances of fertilization are
higher. Ovulation roughly occurs in the middle of
menstruation i.e. about 13th or 15th day of menstrual
cycle. Fertility period is up to 48 hours after
ovulation. Preventing sex during fertility period can
prevent conception. Ovulation period can be
diagnosed as the temperature of the body dips to below average and then rises by about 1oF,
remaining there for the rest of the cycle.
During fertility period cervical mucus is slippery
and can be drawn into a thread when stretched
between two fingers. Another test called as I-sure is
also available in market to know the fertility period.
Period prior to ovulation is safe for copulation.
period after 4th day of temperature rise is also safe.
It is always better to avoid sex from day 10 to day 17
of the menstrual cycle. This method is called as
periodic abstinence.
ii) Withdrawal method/ coitus interreptus: this is the old
method of birth control which was in use about 2000
years ago. It involves the withdrawal of penis from
the female urinogenital tract before ejaculation so
that sperms are not deposited in the female’s vagina.
This method does not work always as there may be
delay in withdrawal of penis.
iii) Lactation amoenorrhoea : just after the parturition
there is the phase of absence of menstruation or
amoenorrhoea. It is actually the phase of intense
lactation. Breast feeding the child prevents
conception. But this method works hardly up to six
months.2)Barrier method: these are the mechanical devices
which prevent the deposition of sperms in the vagina
and their passage to uterus, hence prevent the
fertilization. Further they can be inserted by the user in
complete privacy without any help of a medical
practitioner or surgeon. Common barriers are condoms,
diaphragms, fem shield and cervical cap.
i) Condom: This is a thin sheath usually made up of
rubber to cover the penis. It also prevents people
from spreading STDs.
ii) Diaphragm: it is tubular sheath with a flexible
metal or a spring ring which is fitted in vagina.
iii) Fem sheath: the device is polyurethane pouch
with rings at either side. Inner ring is smaller and
present on inner closed side. It is used as female
condom.
iv) Cervical cap and vault cap : cervical cap is a
rubber nipple which is fitted over cervix and is
designed to remain there by suction. On the other
hand vault cap is a hemisphere dome like rubber or
plastic cap with a thick rim meant for fitting over
cervix.
3)Chemical methods: These are the contraceptives which
contain spermicide chemicals. Chemical contraceptives
are in the form of creams, foam, tablets, gel etc. They
commonly contain lactic acid, Boric acid, citric acid, zinc sulphate and potassium permanganate. These
contraceptives are introduced into vagina, prior to
copulation
Sponge is now a foam suppository or tablet containing
Non-oxynol-9 as spermicide. It is moistened before use to
activate spermicide. The device also absorbs ejaculate.
4)Intra-uterine devices: They are the devices made up of
plastic, metal or both which are inserted into female’s
uterus to prevent conception. These may be loops,
spirals, rings, bowls, shields, or T’s. IUDs are generally
categorized into three main classes viz Inert IUDs,
Copper releasing IUDs, and hormone releasing IUDs.
These devices generally contain spermicides and
chemicals capable of killing a sperm.
5)Oral contraceptives: they are the contraceptive
preparations containing progestin either alone or with
combination of oestrogen. Pills are taken orally for 21
days in a menstrual cycle starting from day 5 to day 25,
and then it is restarted after 7 days for next phase.
These act mainly by four ways: a) inhibition of
ovulation, b) alternation of endometrium so as to make
it unsuitable for implantation, c) change in the cervical
mucus so as to prevent passage of sperms through
cervix, d) inhibition of motility and secretion phase of
fallopian tubes. Examples of oral pills are Mala D, Mala L
etc.6)Injectable contraceptives: Two types of injectable
contraceptive preparations are used usually viz depot-
medroxy progesterone acetate(150mg/300mg), or
norethisterone enanthate (200mg).
7)Implants: they are hormone containing devices which
are implanted sub-dermally for long term
contraception. Norplant is an implant device with six
small permeable capsules which are implanted in the
skin in the fan-shaped manner. These contain progestin
which is slowly diffused into tissues and help in
contraception. These works for about 5 years.
8)Surgical methods: these are the permanent methods of
contraception. Methods are operative procedures which
block the passage of semen in males and ova in females.
Techniques are called as sterilization methods. These
include vasectomy and tubectomy. Vasectomy is the
procedure in which vasa deferentia is cut and occluded
so as to block the passage of sperms. On the other hand
in tubectomy oviducts are cut and ligated.
Medical termination of pregnancy: it is the
deliberate abortion of child in which pregnancy is
damaged before the full term of gestation period.
Almost 20% of total world pregnancies are aborted.
Number of medical termination of pregnancy is about
40-50 million per year. In India there is a law and a
proper act has been developed regarding the MTP,Medical Termination of Pregnancy act 1971. These are
usually performed after amniocentesis and Sonography,
in conditions like rape, unwanted pregnancy, and
malformed children.
Infertility:
It is an inability of producing young ones after about 1-2
years of regular and unprotected sex. Unlike sterility it
is not a complete inability to produce young ones. It
may also be defined as relative sterility. It may be of two
types viz primary infertility and secondary infertility.
Primary infertility is a type of infertility in which
parents have never had children. On the other hand in
secondary infertility is present in patients who have
previously had children. Infertility may be present in
males as well as females.
Infertility in males: semen is about 3-4 ml per
ejaculation with the sperm count of about 200 million,
mostly motile, with proper fructose content and fluidity
which is deposited high up in the vagina.
Any defect in the sperm count, structure, sperm
motility, and seminal fluid can lead to infertility. Low
sperm count is called as Oligospermia, while absence of
sperms is called as azospermia. Low sperm motility is
called as asthenozoospermia. Defective sperm
morphology is called as teratozoospermia.
There are various causes for infertility such as : 1)Cryptorchidism or failure of testes to descend into
scrotum. It it caused azospermia.
2)Absence or blockage of vas deference or vasa
efferentia.
3)Loss of ciliary movement and sperm motility.
4) Hyperthermia or high scrotal temperature due to
varicose veins, tight and warm undergarments etc.
5)Infection, like mumps after puberty, bronchiectasis,
seminal vesicle and prostate infections.
6)Alcoholism.
7)Klinfilter’s syndrome.
8)Gonadotropin deficiency.
9)Cytotoxic drugs, radiations, antidepressants, and
anticonvulsants.
10) Ejaculatory defects which
cause failure to deposit sperms high up in the
vagina.
Infertility in females: females may have
infertility due to various causes as follows:
1)Anovulation and oligo-ovulation are caused by
ovarian cysts, deficient functioning of hypothalamo-
pituitary complex or by thyroid or adrenal defect.
2)Inadequate growth and functioning of corpus luteum
resulting in in reduced progesterone secretion and secretory changes in endometrium which inhibits the
implantation.
3)Ovum not released, instead remain trapped in in
follicle.
4)Oviducts may fail to take up the ovum from ovary.
5)Non canalization of uterus.
6)Defects in cervix or vagina.
There are various other factors for infertility in
females.
Treatment of infertility: male infertility is corrected
by avoidance of alcohol, avoidance of tight and warm
undergarments, cold scrotal baths twice a day. Use of
vitamin E, C, B12 , and folic acid.
Use of clomiphene, orally or giving HCG (Human Chorionic
Gonadotropin) intramuscularly. Testosterone can also be
prescribed. If antisperm antibodies are present in the semen,
dexamethasone is administered.
If testes are not decent into scrotum or vasa deferentia is
blocked or cut, patient is to be operated
In females ovulation is low or absent, it may be induced by
clomiphene citrate, HMG (Human Menopausal
Gonadotropin), FSH (Follicle stimulating hormone), etc.
cysts, lockage or cut oviducts or ovaries are corrected by
surgery, ovarian diathermy, and laser vaporization etc.Assisted reproductive technologies.
Assisted Reproductive Technologies /ART:
It is a group of special techniques that help in reproduction
in the infertile couples by retrieving oocyte from ovary or
sperms from testes bringing about artificial insemination
and development of embryo. Different procedures of ART
are as under:
Artificial Insemination: it is brought about by semen
either from husband or donor. Semen is washed out;
centrifuged, concentrated motile sperms are collected. About
0.3ml of semen with at least 1 million sperms is required. It
is inserted into female’s vagina or uterus.
If the sperms were collected from husband, technique is
named as Artificial Insemination Husband. On the other
hand if husband’s sperms are defective. Sperms are collected
from a donor the technique hence is called as Artificial
Insemination Donor.
Surrogate mother: if the mother is unable to bear the
children due to malformed uterus, a surrogate mother can
be hired to bear children through IVF –ET.
In Vitro Fertilization –Embryo Transfer:
in vitro fertilization is the technique of fertilization carried
out in a container outside the mother’s uterus. Embryo transfer is the technique where implantation of a young
embryo is carried out in to uterus of mother after the
embryo has been prepared outside the body.
Various steps involved are as follows:
1)Induction of superovulation: several drugs are
administered for induction of super ovulation so that
more than one, ova are produced. These drugs include
clomiphene citrate, Human Menopausal Gonadotropin,
Follicle stimulating hormone, etc.
2)Monitoring follicular growth: follicular growth is
monitored by Sonography or serum estradiol estimation.
When follicle reaches more than 18 mm in diameter or
serum estradiol reaches about 250pg/ml per follicle,
HCG human chorionic gonadotropin is administered.
3)Oocyte retrieval: 36 hours after HCG administration
mature oocytes are retrieved either by abdominal
laproscopy or by sonographic procedure.
4)Maintenance of eggs: Mature oocytes are put in the
culture medium with nutrients. They are examined so
that mature oocyte can be easily separated from
immature ones. It is kept in the incubator for about 4-6
hours.
5)Semen selection: semen is purified and concentrated.
About 50,000-100000 sperms are required.6)Fertilization: Purified sperms are poured over the
mature selected oocyte. If the sperm count is less then
single sperm is injected in ovum by intra-cytoplasmic
sperm injection technique. As the fertilization occurs
outside the mother’s body it is called as in vitro
fertilization.
7) Separation of fertilized eggs: the fertilized eggs are
separated and allowed to remain in culture medium
maintained in incubator for 48-72 hours. Fertilized eggs
reach the 4-8 celled stages.
8)Embryo transfer: 4-8 celled embryo is transferred into
female’s uterus close to the fundus.
9)Luteal phase support: for next 14 days progesterone is
provided to mother for the maintenance of pregnancy.
10) Pregnancy test: After 14
days, pregnancy is tested, so that success of the
procedure is ensured.
GIFT (Gamete Intra Fallopian Transfer): it is a
technique in which two retrieved unfertilized eggs and 2.5
lakh fully motile sperms are transferred to fallopian tube
through laparoscopy.
( ZIFT) Zygote Intra Fallopian Transfer: it is the
technique in which one day old zygote is transferred to
fallopian tube of the female by laparoscopy or uterine
ostium under ultrasonic guidance.
It is an inability of producing young ones after about 1-2
years of regular and unprotected sex. Unlike sterility it
is not a complete inability to produce young ones. It
may also be defined as relative sterility. It may be of two
types viz primary infertility and secondary infertility.
Primary infertility is a type of infertility in which
parents have never had children. On the other hand in
secondary infertility is present in patients who have
previously had children. Infertility may be present in
males as well as females.
Infertility in males: semen is about 3-4 ml per
ejaculation with the sperm count of about 200 million,
mostly motile, with proper fructose content and fluidity
which is deposited high up in the vagina.
Any defect in the sperm count, structure, sperm
motility, and seminal fluid can lead to infertility. Low
sperm count is called as Oligospermia, while absence of
sperms is called as azospermia. Low sperm motility is
called as asthenozoospermia. Defective sperm
morphology is called as teratozoospermia.
There are various causes for infertility such as : 1)Cryptorchidism or failure of testes to descend into
scrotum. It it caused azospermia.
2)Absence or blockage of vas deference or vasa
efferentia.
3)Loss of ciliary movement and sperm motility.
4) Hyperthermia or high scrotal temperature due to
varicose veins, tight and warm undergarments etc.
5)Infection, like mumps after puberty, bronchiectasis,
seminal vesicle and prostate infections.
6)Alcoholism.
7)Klinfilter’s syndrome.
8)Gonadotropin deficiency.
9)Cytotoxic drugs, radiations, antidepressants, and
anticonvulsants.
10) Ejaculatory defects which
cause failure to deposit sperms high up in the
vagina.
Infertility in females: females may have
infertility due to various causes as follows:
1)Anovulation and oligo-ovulation are caused by
ovarian cysts, deficient functioning of hypothalamo-
pituitary complex or by thyroid or adrenal defect.
2)Inadequate growth and functioning of corpus luteum
resulting in in reduced progesterone secretion and secretory changes in endometrium which inhibits the
implantation.
3)Ovum not released, instead remain trapped in in
follicle.
4)Oviducts may fail to take up the ovum from ovary.
5)Non canalization of uterus.
6)Defects in cervix or vagina.
There are various other factors for infertility in
females.
Treatment of infertility: male infertility is corrected
by avoidance of alcohol, avoidance of tight and warm
undergarments, cold scrotal baths twice a day. Use of
vitamin E, C, B12 , and folic acid.
Use of clomiphene, orally or giving HCG (Human Chorionic
Gonadotropin) intramuscularly. Testosterone can also be
prescribed. If antisperm antibodies are present in the semen,
dexamethasone is administered.
If testes are not decent into scrotum or vasa deferentia is
blocked or cut, patient is to be operated
In females ovulation is low or absent, it may be induced by
clomiphene citrate, HMG (Human Menopausal
Gonadotropin), FSH (Follicle stimulating hormone), etc.
cysts, lockage or cut oviducts or ovaries are corrected by
surgery, ovarian diathermy, and laser vaporization etc.Assisted reproductive technologies.
Assisted Reproductive Technologies /ART:
It is a group of special techniques that help in reproduction
in the infertile couples by retrieving oocyte from ovary or
sperms from testes bringing about artificial insemination
and development of embryo. Different procedures of ART
are as under:
Artificial Insemination: it is brought about by semen
either from husband or donor. Semen is washed out;
centrifuged, concentrated motile sperms are collected. About
0.3ml of semen with at least 1 million sperms is required. It
is inserted into female’s vagina or uterus.
If the sperms were collected from husband, technique is
named as Artificial Insemination Husband. On the other
hand if husband’s sperms are defective. Sperms are collected
from a donor the technique hence is called as Artificial
Insemination Donor.
Surrogate mother: if the mother is unable to bear the
children due to malformed uterus, a surrogate mother can
be hired to bear children through IVF –ET.
In Vitro Fertilization –Embryo Transfer:
in vitro fertilization is the technique of fertilization carried
out in a container outside the mother’s uterus. Embryo transfer is the technique where implantation of a young
embryo is carried out in to uterus of mother after the
embryo has been prepared outside the body.
Various steps involved are as follows:
1)Induction of superovulation: several drugs are
administered for induction of super ovulation so that
more than one, ova are produced. These drugs include
clomiphene citrate, Human Menopausal Gonadotropin,
Follicle stimulating hormone, etc.
2)Monitoring follicular growth: follicular growth is
monitored by Sonography or serum estradiol estimation.
When follicle reaches more than 18 mm in diameter or
serum estradiol reaches about 250pg/ml per follicle,
HCG human chorionic gonadotropin is administered.
3)Oocyte retrieval: 36 hours after HCG administration
mature oocytes are retrieved either by abdominal
laproscopy or by sonographic procedure.
4)Maintenance of eggs: Mature oocytes are put in the
culture medium with nutrients. They are examined so
that mature oocyte can be easily separated from
immature ones. It is kept in the incubator for about 4-6
hours.
5)Semen selection: semen is purified and concentrated.
About 50,000-100000 sperms are required.6)Fertilization: Purified sperms are poured over the
mature selected oocyte. If the sperm count is less then
single sperm is injected in ovum by intra-cytoplasmic
sperm injection technique. As the fertilization occurs
outside the mother’s body it is called as in vitro
fertilization.
7) Separation of fertilized eggs: the fertilized eggs are
separated and allowed to remain in culture medium
maintained in incubator for 48-72 hours. Fertilized eggs
reach the 4-8 celled stages.
8)Embryo transfer: 4-8 celled embryo is transferred into
female’s uterus close to the fundus.
9)Luteal phase support: for next 14 days progesterone is
provided to mother for the maintenance of pregnancy.
10) Pregnancy test: After 14
days, pregnancy is tested, so that success of the
procedure is ensured.
GIFT (Gamete Intra Fallopian Transfer): it is a
technique in which two retrieved unfertilized eggs and 2.5
lakh fully motile sperms are transferred to fallopian tube
through laparoscopy.
( ZIFT) Zygote Intra Fallopian Transfer: it is the
technique in which one day old zygote is transferred to
fallopian tube of the female by laparoscopy or uterine
ostium under ultrasonic guidance.
Sex determination :-:Establishment of sex through differential development in an individualan at early stage of life is called as sex determination.
(Additional Information)History of Sex Determination ::-
How an individual's sex is determined has been one of the most studied question in the history of embryology. Aristotle who collected and dissected embryos claimed that sex was determined by heat of male partner during sexual intercourse. Thus more heated the passion, Greater the probability of offspring to be male. Aristotle told that women were fundamentally men whose development was arrested too early. The female was mutilated male whose development had stopped because the coldness of mother's womb overcame the heat of the Father's semen. Women were therefore considered more colder and passive than men and female sexual organs had not developed to the point at which they could provide active seeds. This view was accepted by Christian Church and by a renowned author of anatomical textbooks namely Gelan.
The view of Aristotle remained famous over a thousand years. As late as 1543, Andreas vesalius held the view. By the end of 1500 anatomist had rejected Gelan's representation of female anatomy. During 1600s and 1700s females were found to be producing eggs that could transmit parental traits, therefore physiology of sex organs began to be studied.Until late 20th century environment was believed to be important in determining sex. In 1905, correlation of female sex with XX sex chromosome and of me sex with XY sex chromosomes was established. This finding suggested strongly that specific nuclear component was necessary for detecting the development sexual phenotype.
Methods of sex determination( compulsory part) :-
There are both environmental as well as internal mechanisms of sex determination those can be operated in different species.
Four main modes of sex determination are as:
1) Environmental Sex determination
2) Allosomic sex determination
3) Non-allosomic sex determination
4) Haplodiploidy
Environmental Sex determination:- It is a non genetic mode of sex determination in which environmental conditions determine the sex of the offspring. Organisms are capable to develop into any of the two possible sexes. Eg. In marine worm Bonellia,larva develops into female if it settles down alone in an isolated place . Any larva coming in contact with already developed female remains small and develops into a male. It enters the body of female and lives in its uterus as a parasite.
In crocodiles low temperature is responsible to induce female characters into a larva while as high temperature induces maleness. In turtles temperature below 28° C induces maleness and above33°C induces female Ness in larvae. If temperature is between 28°C and 33°C equal umber of male and female offspring are developed.
Non- Allosomic Genetic Sex determination:- In this type of sex determination, fertility factor is present in the non- Allosomes. In Chlamydomonas the genes controlling male and female characters more technically (+) and ( -) characters are regulated by the genes those are present in the Autosomes. In maize sex chromosomes are absent. There are two separate genes. One determines the development of male inflorescence while other is responsible for development of female inflorescence on the cob.
Allosomic Genetic Sex Determination:- in this type sex is determined by specific chromosomes called as Sex chromosomes or Allosomes. Sex chromosome in the form of X body was first seen in fire fly by Henking in 1891. In 1902 Stevens discovered Y chromosome. Late in 1905 Steven and Wilson gave chromosomal theory of sex determination with two types of sex chromosomes X and Y.
Types of Allosomic sex determination are as under:
(Important question)1) XX-XY type of sex determination ( Sex determination in human beings):-
The female in this type of sex determination female is homomorphisms with two similar sex chromosomes,XX. Male is heteromorphic containing two types of sex chromosomes XY. Y chromosome is shorter in length than X chromosome and is morphologically different. Despite difference in morphology X and Y chromosomes synapse during cell cycle. The synapsing part is called as homologous region and the region which does not synapse is called as differential region. Genes present in homologous region are similar and are called XY linked genes. Sex if the baby is determined by type of sperm that fuses with the egg. Female is homogametic and produces only one type of eggs with XY chromosomes. Male is heterogametic and produces two types of sperms 50% of sperms contain X chromosomes and 50% of the sperms contain Y chromosomes. If sperm contains Y chromosome along with 22 Autosomes, such sperm is called as androsperm(22+Y). On the other hand when sperm contains X chromosome with 22 Autosomes such sperm is called as gynosperm(22+X).
If androsperm fuses with the egg sex of the offspring will be male. On the other hand if gynosperm fuses with the egg,sex of the offspring is female. Such a method of sex determination is called as male heterogamety.
2) XX -XO type of sex determination :- This mode of sex determination is found in round worms,grasshoppers, cockroaches,true bugs and some plants viz Vellisneria and Discorea Females contain two similar sex chromosomes XX. Therefore they are homogametic producing single type of gametes Autosomes A + sex chromosome X i.e (A+X). Males possess only one sex chromosome. X chromosome present in male is similar to that present in females. Males are heterogametic forming two types of gametes viz (A+X) gynosperm and (A+O) androsperm. Fusion of androsperm (A+O) with an egg forms male offspring while as fusion of gynosperm (A+X) with an egg forms female offspring.
(Important question)3) ZW-ZZ sex determination or sex determination in birds:- This method of sex determination occurs in birds,some reptiles, fished and some plants. Both sexes male as well as female have two sex chromosomes. However the female hasheteromorphic sex chromosomes (ZW) while males have homomorphic sex chromosomes (ZZ). Females produce two types of eggs , male forming (A+Z) and female forming (A+W). Male produces similar type of gametes with (A+Z) chromosomes. Unlike human beings where male sex determine the sex of child,in birds sex of the offspring is dependent upon female gamete. Such type of sex determination is called as female heterogamety.
4) ZO-ZZ sex determination (Sex determination in butterflies and moths):- females of butterflies and moths possess a single sex chromosome (AA+ZO) while as males have two sex chromosomes (AA+ZZ). Males are homogametic producing single type of gametes (A+Z). On the other hand females produce two types of gametes male producing (A+Z) and female producing (A+O).
5) Haplodiploidy(Sex determination in honey bees):-(important question) In this type of sex determination one sex is Haploid while as other is diploid .
Female is diploid which is formed by fusion of two Haploid gamete cells. On the other hand male is Haploid which is formed directly from unfirtilized eggs. As the egg directly gives rise to male offspring so the process is called as arrhenotoky , arrhenotokous parthenogenesis or Haploid parthenogenesis.
In honey bees, female is diploid while as the males are Haploid. Males develop through arrhenotokous parthenogenesis or Haploid parthenogenesis. Male honey bees or drones produce sperms through mitosis. They are stored by female after receiving during the nuptial flight. The female produces Eggs through meiosis. They are fertilized by the stored sperms to produce female offspring. When required one cell is enlarged and the female offspring is fed on royal jelly to convert them into queen. All other females are fed over by been bread. They are changed into sterile workers. While all workers and Queen have both mother and father, drones or males have neither father nor they have sons, they only have grandfather's and grandsons.
Reproductive health:
Reproductive health is a state of physical, emotional,
behavioral and social fitness for leading a responsible, safe
and satisfying reproductive life. Briefly speaking,reproductive life refers to the healthy reproductive organs
with normal functioning. WHO has defined reproductive
health as total wellbeing in all aspects of reproduction i.e. its
emotional, social and behavioral one. A society will be
reproductively healthy if its members possess not only
physically and functionally normal reproductive organs but
also have normal emotional and behavioral interactions
among them in all sex related aspects.
Significance of reproductive health:
1)Awareness is provided to both males and females to
lead healthy and satisfactory reproductive life.
2)Making mature individuals of the society aware of
fertility regulating methods.
3)Providing information so as to keep proper hygiene of
genitalia.
4)Protection is made possible against the STDs.
5)Planning children to the limit of enjoying family life.
6)Obtaining treatment for reproductive diseases at the
early stage.
Problems and strategies
Involved in reproductive health
Problems:
i) Taboos:- usually in several country including India,
religions, traditions, and social set up do not allow much
sharing of knowledge about reproductive health to the
children.
ii) Early marriage:- children were often married in early
stages when they were kids.
iii) Kid parents:- early marriages often lead to the
condition in which kids become parents. They are not
well prepared physically as well as mentally to coup up
with such conditions.
iv) Career:-After marriage it becomes impossible to
children to pursue higher degrees and a prosperous
career. So the career of the married kids may be spoiled.
v) Teenage lady:-The married teenagers are not
physically and mentally fit to have children. It often
leads to the life threatening conditions.
vi) Deformities:- children of early marriage often have the
risk of malformations and deformities.
vii) Neonatal and Maternal Death rates:-Maternal
mortality rate as well as neonatal mortality rate is
usually high in case of child marriages.
viii) Personal hygiene :- Carelessness of maintaining
personal hygiene and hygiene of reproductive organs
results in catching up STDs.
ix) Health of ladies:- Due to early marriage and becoming
parent in early life causes weakness of lady. She
becomes anaemic and prone to infections.
x) Population growth:- after all above discussed problems
caused due to the early marriage there is a serious
threat of population explosion as the population growth
is increasing day by day.
Strategies:- In 1951 India initiated family planning and
hence became the first country to initiate the planning and
programs to improve reproductive health. Program became
successful so India started another program under the name
Reproductive and Child Health Care (ICH) in 1997, which
was more comprehensive than the previous one. It was
based on three main goals viz Reproductive health, child
care and fertility regulation. All these goals may be fulfilled
by adapting few strategies as discussed below:
1)General awareness:-Various organizations including
Govt. and Non Govt. organizations are involved in
providing awareness to the people regarding
different aspects of reproductive health, through
print media, electronic media, social media, seminar
and other programs.
2)Elders:- elders including teachers, parents, and
religious heads are responsible to provide knowledge
and awareness about sex related aspects andparticularly sex related problems and drawbacks of
early sexual relationships.
3)Sex education:-it has been and should be added to
the curriculum at high school and college levels so as
to provide sound knowledge about reproductive
health to the younger generation. It will help in
reducing myths, miss beliefs and threats regarding
various sex related problems, and will provide
knowledge to make children know the consequences
of indulgence in early sexual relationships.
4)Family welfare information:- All persons at the
marriageable age should have information regarding
birth control options, reasons of failure to conceive(
to have children), Care of would-be-mother, post
natal care of mother and child, importance of breast
feeding etc.
5)Uncontrolled population :- It is necessary to aware
the married couples about consequences of
overpopulation.
6)Social evils and crimes:- information should be
spread about sex abuses and crimes.
7) Infrastructure:-Proper infrastructure should be
provided besides the expertise and material support
for attaining reproductive health through providing
assistance in sex related problems like pregnancy,
delivery, contraception, infertility and STDs.8) Sex determination:- It is a strategy by which sex of
the child can be checked before birth through
amniocentesis or Sonography. Nowadays there is ban
on both the processes.
9) Marriageable Age:- Marriageable age has been fixed
as 21 years for boys and 18 years for girls.
10) Research:- Researches are still going on to design
new techniques and methods of contraception. For
instance Central drug research institute (CDRI)
luknow has developed “saheli” a new steroid,
contraceptive one week pill.
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