Menstrual Cycle

The initiation of the first menstrual cycle at puberty in human females is termed menarche. Permanent cessation around age 50 is known as menopause.

All statements are correct except B. The first menstrual cycle begins at puberty and is called menarche, not menopause.

The corpus luteum secretes large amounts of progesterone, which is essential for maintenance of the endometrium.

If fertilisation does not occur the corpus luteum degenerates. The fall in progesterone causes the endometrium to break down, giving menstrual flow.

A menstrual cycle of about 28 days has: the menstrual phase (days 1–5), the follicular or proliferative phase (up to day 13), ovulation (about day 14) and the luteal phase (days 15–28).
After ovulation the ruptured Graafian follicle changes into the corpus luteum, which secretes large amounts of progesterone.
Under progesterone the endometrial glands become secretory to prepare for implantation, so this phase is called the secretory phase; it is the same as the luteal phase.
It extends from about day 15 to day 28, i.e., it lasts for about 13–14 days.
The follicular phase is the proliferative phase, not the secretory phase.
Hence the secretory phase is the luteal phase and lasts for about 13 days.

During the follicular phase the secretion of gonadotropins (LH and FSH) increases gradually and stimulates follicular development and oestrogen secretion.
Both LH and FSH attain a peak in the middle of the cycle, i.e., about the 14th day of a 28-day cycle.
This rapid secretion of LH leading to its maximum level is called the LH surge.
The LH surge induces rupture of the Graafian follicle and release of the ovum (ovulation).
Hence the LH surge normally occurs about the 14th day.

After ovulation the remaining part of the Graafian follicle changes into the corpus luteum, which secretes large amounts of progesterone essential for maintaining the endometrium. This is the luteal or secretory phase. So this matching is correct.
Menstruation is due to the breakdown of the endometrial lining of the uterus and its blood vessels; the myometrium (the muscular layer) does not break down.
At ovulation LH and FSH do attain peak levels, but progesterone is not falling sharply then; it rises afterwards, when the corpus luteum forms.
In the proliferative (follicular) phase it is the endometrium that regenerates, not the myometrium.
Hence the correct matching is development of corpus luteum – secretory phase and increased secretion of progesterone.

Menstrual fluid consists of blood, mucus and the broken down endometrial tissue of the uterus.
Menstrual blood does not clot easily. The fibrin formed is broken down by the enzyme fibrinolysin (plasmin) released from the degenerating endometrium, so the fluid normally stays liquid.
So the statement that the menstrual fluid can easily clot is incorrect.
The first menstruation, which begins at puberty, is called menarche; this statement is correct.
About 40 ml of blood (roughly 30 to 80 ml) is lost in a normal menstruation; this statement is correct.
At menopause the ovaries stop responding and oestrogen falls, so the negative feedback on the pituitary is removed and the gonadotropins (FSH and LH) rise sharply; this statement is also correct.

After ovulation the ruptured follicle forms the corpus luteum, which secretes large amounts of progesterone.
Progesterone is essential for the maintenance of the thickened, secretory endometrium of the uterus.
If fertilisation does not occur, the corpus luteum degenerates towards the end of the cycle.
The level of progesterone in the blood then falls sharply.
Without progesterone the endometrium cannot be maintained; it disintegrates and is shed along with blood, which is menstruation.
The fall of oestrogen also contributes, but the immediate cause is the withdrawal of progesterone.
So the hormone is progesterone.

If the ovum is not fertilised, the corpus luteum degenerates (disintegrates) towards the end of the luteal phase; this is likely.
With the degeneration of the corpus luteum, the secretion of progesterone declines rapidly; this is likely.
The corpus luteum also secretes oestrogen, so the oestrogen level falls further; this is likely. The fall of these hormones leads to menstruation.
Primary follicles are formed in the ovary during foetal life, and their numbers only decline afterwards; no new primary follicles are formed in the adult.
According to the answer key, the statement that a primary follicle starts developing is therefore the unlikely one; what begins in the next cycle under FSH is the growth of already existing follicles into Graafian follicles.
Note: some books treat the start of development of a new follicle as a normal event after failure of fertilisation, so this question is open to interpretation.

The menstrual cycle (about 28 days) has a menstrual phase (days 1–5), a follicular or proliferative phase (days 5–14) and a luteal or secretory phase (days 15–28).
During the proliferative phase, the Graafian follicle grows and secretes estrogen, which rebuilds the endometrium.
Around day 14, a surge of LH (with FSH) causes the Graafian follicle to rupture and release the secondary oocyte. This is ovulation.
After ovulation the follicle becomes the corpus luteum and the secretory phase begins.
So ovulation normally takes place at the end of the proliferative phase (around the middle of the cycle).

The menstrual cycle is controlled by hormones of the pituitary and the ovary.
FSH (follicle stimulating hormone) stimulates the growth of ovarian follicles, which secrete estrogen.
Estrogen causes proliferation of the endometrium. A peak of LH (luteinising hormone), together with FSH, causes ovulation and formation of the corpus luteum, which secretes progesterone.
So the cycle is controlled mainly by FSH, LH and estrogen together (with progesterone in the luteal phase); a single hormone alone cannot control it.
So the answer is FSH, LH and estrogen.