NCERT Solutions for Class 12 Biology Chapter 3

High temperature of abdomen kills the spermatogenic tissue of the testes, so no sperm are formed.

40 sperms, 10 eggs.

LH surge refers to maximum level of luteihising hormone living middle of menstrual cycle. LH couses ovulation.

(i) Germinal epithelium have two types of cells.
1. Spermatogonium.
2. Sertoli cells
(ii) Leydig’s cell or Interstitial cells.

Functions of the Testis They produce male gametes called spermatozoa by the process of spermatogenesis. The leydig cells of the seminiferous tubules secrete the male sex hormone called testosterone. Testosterone aids the development of secondary sex characteristics in males. Functions of the ovary They produce female gametes called ova by the process of oogenesis. The growing Graffian follicles secrete the female sex hormone called estrogen. Estrogen aids the development of secondary sex characteristics in females.

Follicle-stimulating hormones (FSH) and luteinizing hormones (LH) are secreted by gonadotropin releasing hormones from the hypothalamus .These hormones are involved in the regulation of the process of spermatogenesis. FSH acts on sertoli cells, whereas LH acts on leydig cells of the testis and stimulates the process of spermatogenesis.

Spermiogenesis It is the process of transforming spermatids into matured spermatozoa or sperms. Spermiation It is the process when mature spermatozoa are released from the sertoli cells into the lumen of seminiferous tubules.

Semen (produced in males) is composed of sperms and seminal plasma. The major components of the seminal plasma in the male reproductive system are mucus, spermatozoa, and various secretions of accessory glands. The seminal plasma is rich in fructose, calcium, ascorbic acid, and certain enzymes. It provides nourishment and protection to sperms.

Parturition is the process of giving birth to a baby as the development of the foetus gets completed in the mother’s womb. The hormones involved in this process are oxytocin and relaxin. Oxytocin leads to the contraction of smooth muscles of myometrium of the uterus, which directs the full term foetus towards the birth canal. On the other hand, relaxin hormone causes relaxation of the pelvic ligaments and prepares the uterus for child birth.

Dogs and rodents are polyovulatory species. In these species, more than one ovum is released from the ovary at the time of ovulation. Hence, six eggs were released by the ovary of a female dog to produce six puppies.