B. Sexual reproduction in human being :
- Men have XY sex-chromosomes and women have XX sex-chromosomes.
- X-chromosome is present in men and women.
- Y-chromosome is present in men only.
- Male reproductive system of humans consists of
- testes,
- various ducts and
- glands.
- Testes are present in the scrotum, outside the abdominal cavity.
- Testes contain numerous seminiferous tubules.
- Germinal epithelium present in the tubules divide by meiosis to produce sperms.
- Those sperms are sent forward through various tubules.
- Sequence of those tubules is as-
- rete testis
- vas eferens
- epididymis
- vas deferens
- ejaculatory duct and
- urinogenital duct.
- As the sperms are pushed forwards from one duct to next, they become mature and able to fertilize the ovum.
- Seminal vesicles secrete their secretion in ejaculatory ducts.
- Postate gland and Cowper’s glands secrete their secretions in urinogenital duct.
- Semen is formed of sperms and secretions of all these glands.
- Semen is ejaculated out through penis.
- All the organs of male reproductive system are paired except urinogenital duct, prostate gland, penis & scrotum.
Surprising Facts :
- Length of each epididymis is about 6 meters.
- Length of a sperm is about 60 micrometers.
- Such a small sperm has to cross the distance of approximately 6.5 meter while passing out of male reproductive system.
- Sperm needs large amount of energy.
- For this purpose, fructose is present in the semen.
Human female reproductive system :
- All organs of female reproductive system are in abdominal cavity.
- It includes
- a pair of ovaries
- a pair of oviducts
- single uterus and
- a vagina.
- Besides, a pair of Bartholin's gland is also present.
- Generally, every month, an ovum is released in abdominal cavity alternately from each ovary.
- Free end of oviduct is funnel-like.
- An opening is present at the center of it.
- Oocyte enters the oviduct through that opening.
- Cilia are present on inner surface of oviduct.
- These cilia push the oocyte towards uterus.