Q. Which one of the following is the correct matching of the events occurring during menstrual cycle?
(a) Menstruation : Breakdown of myometrium and ovum not fertilised
(b) Ovulation : LH and FSH attain peak level and sharp fall in the secretion of progesterone
(c) Proliferative phase : Rapid regeneration of myometrium and maturation of Graafian follicle
(d) Development of corpus luteum : Secretory phase and increased secretion of progesterone
Solution :
Correct option : D The menstrual cycle consists of four phases:
menstrual phase, proliferative phase, ovulatory phase and secretory phase.
(i) Menstrual Phase (Bleeding phase or menses) : It takes place on days 3-5 in a 28 days cycle. The production of LH from the anterior lobe of the pituitary gland is considerably reduced. Progesterone production is reduced. Production of estrogens is also reduced in this phase. The endometrium of the uterus breaks down and menstruation begins.
(ii) Follicular Phase (Proliferative Phase) : This phase usually includes cycle days 6-13 or 14.The follicle stimulating hormone (FSH) secreted by the anterior lobe of pituitary gland stimulates the ovarian follicle to secrete estrogens. The endometrium becomes thicker as blood vessels become long and coiled.
(iii) Ovulatory Phase: Both LH and FSH attain a peak level in the middle of cyde (about 14th, day). Graafian follicle ruptures releasing the ovum.
(iv) Luteal Phase (Secretory Phase):This phase usually includes cycle days 15 to 28. The corpus luteum secretes large amount of progesterone. Progesterone stimulates the uterine glands to produce increased amount of watery mucus. In the absence of fertilisation, the corpus luteum degenerates. This causes disintegration of the endothelium leading to menstruation marking a new cycle. So, the correct answer is Development of corpus luteum : Secretory phase and increased secretion of progesterone.
