The phases of menstruation

 

Regenerative phase

During the first few days of this phase, the endometrium of the uterus is shed right down to the basal layer and initially, the rising oestrogen level inhibits the follicle-stimulating hormone. The anterior pituitary gland then releases a follicle-stimulating hormone causing several Graafian follicles to fill with fluids and increase in size. This results in rising of the oestrogen hormone circulating the bloodstream.

The alteration in the hormone balance causes new growth of endometrium of the uterus. In the normal event, all the follicles except one fail to mature and degenerate. The follicle which survives reaches a diameter of 1.5-2 cm and rises to the surface of the ovary. If the length of the woman’s menstrual cycle is shorter or longer than 28 days, it is this regenerative phase that is variable.

Ovulation

As a result of its increasing size, the Graafian follicle will rupture, although the rupture is more like a slow leaking of fluid rather than an instant deflation. Relaxing aids the rupture by softening the follicle membrane. With rising oestrogen levels, the LH is released from the anterior pituitary gland resulting in a surge in the mud cycle of both FSH and LH.

With the rupture of the follicle, the ovum is released and this is called ovulation which causes oestrogen level to decrease.

Secretory phase

The rupture of the follicle is now known us the corpus luteum. The corpus luteum begins to increase in size and produce progesterone. This further change in hormone balance stimulates the uterus to prepare its lining for the reception of the fertilized ovum.

Menstrual phase

The ovum is not fertilized, it dies 12- 24 hours and the anterior pituitary gland redraws luteinizing hormone after 14-15 days. Preparation of pregnancy ceases the endometrium shed with the menstrual flow. Some hours before menstrual bleeding, the blood vessels become constricted by the congested endometrial tissues.

Mabel Ankomah