NCERT Solutions for Class 12 Biology Chapter 2 Human Reproduction

Short Note:

• The male reproductive system includes a pair of testes enclosed in the scrotum (which maintains a lower temperature needed for sperm formation), along with accessory ducts and glands.

• Each testis has seminiferous tubules where spermatogenesis occurs, producing sperm with the help of Sertoli cells, while Leydig cells present outside the tubules secrete testosterone.

• A mature sperm has a head with an acrosome (containing enzymes to help penetrate the egg), a middle piece with mitochondria for energy, and a tail for motility.

Short Note:

• The female reproductive system consists of a pair of ovaries, oviducts (fallopian tubes), uterus, cervix and vagina, along with external genitalia.

• Oogenesis begins during foetal development itself, with oogonia forming primary oocytes that remain arrested until puberty, when one egg is usually released per menstrual cycle.

• The menstrual cycle, roughly 28 days long, is regulated by hormones (LH, FSH, oestrogen, progesterone) and includes menstrual, follicular, ovulatory and luteal phases.

Short Note:

• Fertilisation typically occurs in the ampullary region of the fallopian tube, where the sperm fuses with the egg to form a diploid zygote, which undergoes cleavage divisions to form a blastocyst.

• The blastocyst gets implanted in the uterine wall (implantation), and the placenta forms as a vital connection between the mother and the foetus, facilitating nutrient, oxygen and waste exchange.

• Human pregnancy lasts about nine months (approximately 40 weeks), ending in parturition (childbirth), which is induced by hormonal signals, mainly oxytocin, causing strong uterine contractions.