Human Reproduction Test - 44

The female mammals are characterized by cyclic changes in reproductive tract and ovaries, regulated by some hormones (like FSH, LH). For example, in humans during the childbearing years, about every 28 days, one ovarian follicle (Graafian follicle) matures, ruptures and releases its ovum into the peritoneal cavity. This is called as ovulation and it occurs during most menstrual cycles. The term Graafian follicle is used for a mature follicle in the mammalian ovary.

In human females, the tertiary follicle further changes into the mature follicle or Graafian follicle. The secondary oocyte, present inside Graafian follicle, forms a new membrane, called as zona pellucida, surrounding it. The Graafian follicle now ruptures to release the secondary oocyte (ovum) from the ovary by the process, called as ovulation.

Folliculogenesis is the process in which a recruited primordial follicle grows and develops into a specialized Graafian folicle, having two fates, that is either to ovulate its egg into the oviduct at mid-cycle to be fertilized or to die by atresia. Hence, option C is the correct answer.

 Ovaries are females gonads that produce ova and female hormones. The process of formation of a mature female gamete is called as oogenesis, which is markedly different from spermatogenesis. Oogenesis is initiated during the embryonic development stage when a couple of million gamete mother cells (oogonia) are formed within each fetal ovary; no more oogonia are formed and added after birth. These cells start division and enter into prophase I of the meiotic division and get temporarily arrested at that stage called as primary oocytes. Each primary oocyte, then gets surrounded by a layer of granulosa cells and then called as the primary follicle. A large number of these follicles degenerate during the phase from birth to puberty. Therefore, at puberty only 60,000 - 80,000 primary follicles are left in each ovary.

Reinier de Graaf was a Dutch physician, who discovered the follicles of the ovary (known as Graafian follicles), in which the individual egg cells are formed. He was also important for his studies on the pancreas and on the reproductive organs of mammals.

CORRECT OPTION – B
EXPLANATION FOR CORRECT OPTION -

• FSH hormone is secreted by the pituitary gland which is under the control of the hypothalamus.
• FSH is the hormone responsible for the initiation of spermatogenesis and sperm differentiation as its main function.
• It binds with Sertoli cells and spermatogonia and induces its proliferation. 

Inhibin is secreted by the sustentacular (Sertoli) cell of testes. Its major action is the negative feedback control of pituitary FSH secretion i.e., control of spermatogenesis. Androgens stimulate inhibin production and hence regulate spermatogenesis. Thus the correct answer is option D.

In human females, the menstrual cycle starts with the menstrual phase when menstrual flow occurs and it lasts for 3-5 days. The menstrual phase is followed by the follicular phase. During this phase, the primary follicles in the ovary grow to become a fully mature Graafian follicle and simultaneously the endometrium of uterus regenerates through proliferation. The secretion of gonadotropins (LH and FSH) increases gradually during the follicular phase and stimulates follicular development as well as secretion of estrogens by the growing follicles. Both LH and FSH attain a peak level in the middle of the cycle (about 14th day). Rapid secretion of LH leading to its maximum level during the mid-cycle, called as LH surge induces rupture of Graafian follicle and thereby the release of the ovum (ovulation). The ovulation (ovulatory phase) is followed by the luteal phase during which the remaining parts of the Graafian follicle transform as the corpus luteum.

The risk period in the question refers to the time duration in which there are maximum changes of fertilisation and consequent pregnancy. In a normal menstrual cycle of 28 days, both LH and FSH attain a peak level in the middle of cycle (about 14th day). Rapid secretion of LH leading to its maximum level during the mid-cycle called LH surge induces rupture of Graafian follicle and thereby the release of ovum (ovulation). The ovulation (ovulatory phase) is followed by the luteal phase during which the remaining parts of the Graafian follicle transform as the corpus luteum. If the menstrual cycle is of 35 days duration, the LH and FSH will attain peak level in the middle of cycle around 16th or 17th day and hence ovulation should occur on 16th or 17th day. After which ovum shall be available in oviduct for fertilization for 24 hours. If sperms don't arrive then after 24 hours the ovum shall start journey towards uterus. Chances of conception will be maximum if there is sexual intercourse around the middle of menstrual cycle. Thus 16th to 24th day is called a risk period. Before this period there will be follicular phase and after ovulation there will be luteal phase.