Menstrual is the discharge of blood, mucus, endometrium and unfertilized ovum from the uterus after the destruction of an average of 28 days (24-32) in the sexual life of an adult woman. Menstrual cycle is the periodic occurrence of menstruation. The first cycle is called menarche. Menstrual cycle starts at the age of 12-15 years and continues till the age of 45-50 years. It has gonadotropic hormone effect.
The menstrual cycle is divided into 4 phases based on the changes in the endometrium of the uterus. namely-
1. Regenerative/Repairing/Resting Phase: After the end of one menstrual cycle, the endometrium returns to its normal state before another cycle begins. Its duration is 3rd-6th day after onset of menstruation. During this time, FSH and LH hormones are secreted, ovarian follicle growth accelerates and the endometrium becomes 1 mm thick.
2. Proliferative Phase: The phase in which the endometrium grows and ovulation occurs is called the proliferative phase. Its duration is 7th-14th day. During this time estrogen hormone is secreted, ovarian follicles transform and endometrium becomes 3-4 mm thick.
3. Premenstrual Phase: The phase in which the fully formed endometrium contains the blastocyst is called the premenstrual phase. Its shelf life is 15-28 days. During this time progesterone and estrogen hormones are secreted from corpus luteum, nutrients (glycogen, lipids) increase in endometrial cells, endometrium becomes 5-6 mm thick and contains blastocyst.
4. Menstrual/Destructive/Bleeding Phase: In the phase in which blood, mucus, endometrium and unfertilized ovum are destroyed and released into the vagina is called menstruation. If the egg is not fertilized within 36 hours of ovulation, it is destroyed and menstruation occurs. Its shelf life is 4-5 days.
At this time, the secretion of FSH, LH, estrogen and progesterone hormones stops and the corpus luteum is disturbed. The endometrium begins to break down. Arteries and capillaries rupture and bleeding begins. 30-40 ml of fluid is released with each menstruation.