(a) Name the cells that undergo spermatogenesis in humans. Write their specific location and chromosome number.

(b) Describe the process of spermatogenesis up to the formation of spermatozoa

OR

(a) What do ‘oral pills’ contain that makes them act as contraceptives?

(b) Explain the hormonal regulation of menstrual cycle in humans.

(a) The cells that undergo spermatogenesis in humans are immature male germ cells. These immature male germ cells are also known as spermatogonia. Each spermatogonium is diploid and contains 46 chromosomes.

(b) The process of production of sperms from the immature germ cells in males is known as Spermatogenesis.

Male germ cell is known as spermatogonium and it is diploid in nature. The spermatogonium increases in size to form diploid primary spermatocyte during spermatogenesis. Now the diploid primary spermatocyte undergoes first meiotic division to form two equal haploid secondary spermatocytes. This first meiotic division is a reductional division.

Each haploid secondary spermatocytes undergoes second meiotic division to form two equal haploid spermatids.

So, a diploid spermatogonium produces four haploid spermatids, which are transformed into spermatozoa (sperm). This whole process i.e., conversion of spermatogonium to spermatozoa is known as Spermiogenesis.

This process takes place in seminiferous tubules present inside the testes.

OR

(a) ‘Oral Pills’ contains are either progestogens or progestogen-oestrogen combinations.

Estrogen and progestin are two female sex hormones. Combinations of estrogen and progestin work by preventing ovulation. They also change the lining of the uterus to prevent pregnancy from developing and change the mucus at the cervix to prevent sperm from entering.

So ‘Oral Pills’ being combination of Estrogen and progestin acts as contraceptives.

(b) The menstrual cycle is a reproductive cycle in female primates. The whole cycle takes around 28 days to complete.

One ovum is released during the middle of each menstrual cycle.

The menstrual flow is due to breakdown of endometrial lining of the uterus and its blood vessels which forms liquid that comes out through vagina.

The menstrual cycle is regulated by various hormones namely FSH (Follicle Stimulating Hormone), LH (Luteinizing Hormone), Estrogen and Progesterone.

The hormone FSH and LH are secreted from the anterior pituitary gland. During follicular phase of menstrual cycle the level of FSH and LH increase.

The primary follicle is converted into Graafian follicle. This conversion is stimulated by FSH, which is secreted under the influence of RH (releasing hormone) from the hypothalamus.

Now the hormone estrogen is secreted when the level of LH increases gradually, this also leads to the growth of follicle. Now the estrogen starts the secretion of FSH and stimulates the secretion of LH. This in turn causes the thickening of the uterine endometrium.

Due to increase in level of LH, the graafian follicle starts rupturing and releases ovum into the fallopian tube. During luteal phase the ruptured graafian follicle changes to corpus luteum and in turn secretes progesterone hormone.

This progesterone hormone helps to prepare and maintain endometrium for the implantation of the embryo.

The ovulation is inhibited by decrease in secretion of LH and FSH. And the LH and FSH secretion decreases due to the high levels of progesterone hormone in the blood.