Human Reproduction :-
Human beings are nonseasonal breeders ,there is no Oestrus / heat .
- In human reproduction , females has the ability to produce young ones begins at Menarche ( beginning of menses ) and end at Menopause ( stoppage of menses ) .
- In human reproduction , Fertilization is international , there is Viviparous I . e . giving birth to young ones .
- In human reproduction , Foetus develops inside uterus , Infants can be on mother’s milk , parental care is very well developed .
- In the case of human reproduction , Gonads which form gametes are called Primary sex Organs – testis in male and Ovary in females .
- Sex Organs , Glands and Duct do not produce gametes but are other wise essential for Sexual human reproduction are known as secondary sex Organs .
- In human male – secondary sex organs are – Vasa efferentia , Epididymes , Vasa deferentia , Seminal vesicles Ejaculatory duct Urethra ,Prostate gland and Cowper’s glands , Penis .
- In human female – secondary Sex Organs are – Fallopian tubes , Uterus , Vagina , External genitalia , Bortholin’s gland and Mammary glands .
- Human reproduction consists Male Reproductive System and Female Reproductive System .
Male Reproductive System :-
In human reproduction , The male Reproductive System Consists of paired testes , Several Accessory glands , a duct System and a mating Organ called the penis .
In man , both testes normally remain suspended in a pouch called Srotum outside the abdominal cavity .
- Scrotum keeps the testes at cooler temperature than the body temperature , this is essential for the maintenance and function of the spermatogenic tissue of the testes .
- In some seasonally breeding mammals testes descend into the scrotum in the breeding season but ascend back into the abdomen in the non breeding state .
- A typical male has two testes approximately 5 cm long ,3 cm wide , 2.5 Cm thick . weight 10 to 15 gram each testes . These are major components of human reproduction .
- The testes consists following structure –
1 . Tunica :-
The multilayered tunica covers the testes . It facilitate blood supply to the testes and creates a partitions between sperm producing regions of the testes . There are three layers to the tunica .
( a ) Tunica Vasculosa :-
It is the inner layer and consists blood vessels connective tissue .
( b ) Tunica albuginea :-
It is a dense layer of tissue which covers the testes . It also extends into the testes creating partitions between seminiferous tubules where sperm is produced .
( c ) Tunica Vaginalis :-
There are two layers , the parietal and visceral layer . the visceral layer overlies the tunica albuginea ( middle layer of the tunica ) while the parietal layer lines the scrotal cavity .
2 . Seminiferous tubules :-
It lie within the testes and are separated by partitions , the partitions divide the testes into lobules which contain the Seminiferous tubules . They are the site of Spermatogenesis ( Sperm production ) .
- Each lobules contain 1 to 4 Seminiferous tubules and each testis contain up to 900 of these tubules .
3 . Rete testis :-
The Seminiferous tubules open into a series of channels called the Rete testis . The Rete testis facilitate the transport of sperm from testes to the Sperm transport ducts .
4 . Leydig cells ( Interstitial cells ) :-
In the adult male , the soft connective tissues are surrounding the seminiferous tubules contain interstitial cells of Leydig .
The primary function of the cells is production and secretion of androgen ( testosterone ) hormone . Testosterone hormone stimulate Spermatogenesis ( Sperm production ) .
They also provides secondary functions related to giving the male body atypically male appearance including –
Regulation of Central Nervous System , Stimulation of metabolism , maintaining glands and organs in the male Reproductive System . Developing male secondary sexual characters .
5 . Sertoli cells :-
They are found in Seminiferous tubules . They provide Support for germinal cells as they grow and develop into Spermatogonia .
Vasa Efferentia :-
Seminiferous tubules united to form several straight tubules which open into irregular cavity in the posterior part of the testes . Several tubes called Vasa Efferentia arise from the cavity and conduct sperm out from the testes .
Vasa efferentia which arise from each testis and become uniting together to form a folded coiled tube called Epididymis behind each testis .
- The Epididymis stores the sperms temporarily .
- Testes and Epididymis are together called Testicle .
- From each Epididymis , a partially coiled tube called VA’s deferens ascends into the abdomen ,passes over the Urinary bladder and receives the duct from the Seminal vesicle .
- They conduct sperms .
Ejaculatory ducts :-
They are short ( 2 cm ) and straight muscular tube formed by union of a VA’s deferens and duct of Seminal vesicle where ejaculate is formed by mixing of Sperms with secretion of seminal vesicle .
Seminal vesicle :-
They are lobulated , muscular ,glandular part between Urinary bladder and Rectum .
- Each vesicle have a tube that joined VA’s deferens to form Ejaculatory duct .
- Secretion of Seminal Vesicles forms major part of Semen ( 60 – 70 % ) , It is thick , Viscus , alkaline having proteins , fructose ( nourishment for activity of Sperm ) and for stimulating movements in the female tract .
It arises from Urinary bladder and is about 20 cm long .
- Urethra receives the two Ejaculatory ducts to form urinogenital duct .
- Urinogenital duct receives a number of ductules from the Prostate glands .It comes out a membranous part , the membranous part of Urethra receives duct from Cowper’s glands . It then enters Penis as penile part .The opens at the tip of the Penis .
The Penis is a muscular Organ used in mating I . e . Male copulatory Organ which passes out urine .
- It is made up of spongy muscle tissue , when filled with blood , causes stiffening and erection of the Penis .
Prostate gland :-
It is a large pyramidal gland , encloses a part of Urethra .
- It contains 30 – 40 alveoli which open separately into Urethra by fine ducts .
- Secretion of Prostate gland is thick , milky and alkaline , constituting up to 20 – 40 % of Semen .
- It is essential for sperm motility ( Removal causes Sterility ) .
Cowper’s gland / Bulbourethral glands :-
A pair of small glands , 4 – 5 cm below of Prostate gland and opening into membranous Urethra by separate ducts .
- The secretion has abundant mucus for lubrication of Reproductive tract .
Female Reproductive System :-
In human reproduction , female reproductive system consists of pair of Ovaries , a pair of Fallopian tubes , Uterus , Vagina , External genitalia , pair of Bartholin’ s glands and Mammary glands .
One pair of Ovary connected to wall of dorso lateral side of the abdominal Coelom by mesovarium . These are major components of human reproduction .
- The germinal epithelium of Ovary perform Oogenesis whereas Ovary also release two hormones – Oestrogen and Progesterone , after Ovulation Ovum is released into the Coelomic fluid .
The Ovaries are small almond shaped structures , covered by a thick connective tissue capsule the Tunics albuginea , this is covered by a simple squamous mesothelium called Germinal epithelium .
- The Ovary has a cortex where the Ovarian follicles can be found and highly vascular medulla with coiled Arteries .
- The Ovary contains many primordial follicles , which are mostly found around the edge of the Cortex .
- In each Ovarian cycle about 20 Primordial follicles are activated to begin maturation , however normally only one fully matures and the rest contribute to the Endocrine function of the Ovary .
- When first meiotic division completed , the Primary follicle has matured into a Secondary follicle . The second meiotic division then starts and Graafian follicle is formed . this contains a Secondary Oocyte .
Fallopian tubes / Oviducts :-
They are paired , muscular and internally ciliated tubes of 10 – 12 cm length which arise near the Ovary and end of uterus .
- Each Oviduct is differentiated into anterior Fallopian tube and posterior Uterus .
- The Oviduct funnel receives in Coelomic fluid . Both have been completely fuse to form common lumen of Uterus .
- The lower part of Uterus is Cervix which have two aperture internal OS and external OS , Cervix opens into Vagina .
It is pyriform , hollow muscular thickened wall but distensible median structure located above and behind Urinary bladder .
- It is meant for nourishing and development of foetus .
- The empty Uterus is 8 cm x 5 cm x 2 cm and lined by a layer called Endometrium .
- Uterus is differentiated into three part .
1 . Fundus:- Upper part above the opening of Fallopian tubes .
2 . Body :- Main part which is broad above and toppers towards lower side .
3 . Cervix :- Neck of uterus which is connected to body an opening .
It is the short and width canal lined by Stratified epithelium . Its open in Vulva , guarded by two pairs of fold or skin Labia minora is non hairy part .
- Clitoris is small and highly vascularized structure present near the Vulva . It is homologous to the Penis of male .
- The opening of the Vagina remains partially covered by thin ring of tissue called the hymen .However , in the long run it is ruptured due to vigorous physical activities .
- Vagina is female copulatory organ for men’s flow as well as birth canal , it is about 8 cm in length .
Bartholin’ s glands :-
One pair and small glands which open into the Vagina through small duct . The secretion is thick , viscous and alkaline for lubrication and counteracting urinary acidity ( similar to Cowoer’ s glands in male ) .
Mammary gland :-
Mammary gland is a part of human reproduction , each mammary gland consists of 15 – 25 lobules , these lobules secret milk to nourish the new born baby .
- From each lobe lactiferous ducts emerge independently the Nipple which has 15 – 25 openings , each about 0.5 mm in diameter . However the histological structure of Mammary glands varies , depending upon sex , age and physiological state .
- Milk secretion is under the control of anterior Pituitary while milk ejection is under control of Oxytocin of posterior Pituitary .