Human Reproduction

Humans reproduce by the process of sexual reproduction. The male reproductive system consists of a pair of testes, the male sex accessory ducts and the accessory glands and external genitalia. Each testis is made up of about 250 compartments called testicular lobules. Each lobule contains one to three highly coiled seminiferous tubules. Each seminiferous tubule is lined by spermatogonia and Sertoli cells. During sperm formation the spermatogonia undergo meiotic divisions, while Sertoli cells provide nutrition to the dividing germ cells. The Leydig cells present outside the seminiferous tubules synthesise and secrete testicular hormones called androgens. The male external genitalia is called penis. The female reproductive system is made up of a pair of ovaries, a pair of oviducts, a uterus, a vagina, external genitalia, and a pair of mammary glands. The ovaries produce the female gamete called ovum. Some steroid hormones called ovarian hormones are also produced in the ovaries. The female accessory duct consists of the oviducts, uterus and vagina. The process of formation of sperm is called spermatogenesis. A human sperm consists of: a head, neck, a middle piece and tail. The process of formation of mature female gametes is called oogenesis. The reproductive cycle in female is called menstrual cycle. During fertilization, the sperm fertilises the ovum leading to formation of a diploid zygote. After fertilization, the zygote undergoes repeated mitotic division to form a blastocyst. The blastocysts when gets implanted in the uterus, it results in pregnancy. The process of childbirth is called parturition. It is induced by a complex neuroendocrine mechanism involving cortisol, estrogens and oxytocin. Lactation is the process of secretion of milk from mammary glands after childbirth. The secretion of milk is stimulated by the hormone prolactin.

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