what is Menstrual Cycle ?

Menstrual Cycle The reproductive cycle in female primates is known as the menstrual cycle. It starts at puberty which is referred to as menarche. Phases of the Menstrual Cycle The menstrual cycle has 4 phases: (1) Menstrual Phase:

1. The menses take place on cycle days 3-5 in the menstrual cycle.
2. The production of LH is reduced.
3. This leads to degeneration of the corpus luteum and the progesterone production is reduced.
4. Production of oestrogen is also reduced during this phase.
5. The endometrium of the uterus breaks down and the menstruation begins.
6. The menstrual flows have cells of endometrium secretions, blood and unfertilised egg.

(2) Follicular Phase:

1. The follicular phase includes cycle days 6-13 or 14 in a 28 days cycle.
2. The FSH stimulates the ovarian follicle to secrete oestrogens.
3. Oestrogen stimulates the proliferation of the endometrium lining of the uterine wall.
4. The endometrium becomes thick by the rapid multiplication of cell and this is accompanied by an increase in uterine glands & blood vessels.
5. The level of FSH and LH increased

(3) Ovulatory Phase:

1. Both LH & FSH attain a peak level in the middle of the menstrual cycle (about the 14th day).
2. Oestrogen concentration in the blood increases.
3. Rapid secretion of LH ruptures the Graafian follicle and the egg is released.
4. LH leads to ovulation.

(4) Luteal Phase:

1. Luteal phase includes cycle days 15 to 28.
2. Progesterone is secreted by corpus luteum
3. Endometrium wall thickens.
4. Uterine glands become secretory.

Hormonal Control of Menstrual Cycle

1. FSH stimulates the ovarian follicles to produce estrogens.
2. LH stimulates corpus luteum to secrete progesterone.
3. Menstrual phase occurs by the increased production of oestrogens.
4. LH leads to ovulation
5. Proliferative phase occurs due to an increase in the production of oestrogens.
6. Secretory phase occurs due to increased production of progesterone.