The monthly maturation of egg and uterine preparation are collectively called Menstrual cycle. Menstrual cycle is the preparation of the uterus for possible pregnancy. It is controlled by hormones and completed by every 28-days. It is divided grossly into two phases:
- Proliferation Phase
- Menstruation or M-phase
- Follicle or f-phase
- Secretary Phase
- Ovulation or O-phase
- Corpus Luteum or L-phase( if fertilization occurs)
- Menstruation or M-phase: Menstruation is a secondary sexual character of female occurring at puberty. Menstruation is cyclic shedding of endometrium with the passage of blood from broken-down capillaries in spongy and compact layer of endometrium unfertilized ovum and secretions from genital tract. It starts at age of 12-14, continues till childbearing age, and stops usually at the age of 45-50.
- Follicle phase or F-Phase: This phase is of variable duration (14+- 7 days). It starts on first day of menstruation. This phase corresponds to ovarian cycle (proliferation phase) during which oestrogen is produced from granulose cells of ovarian follicles under the influence of FSH from anterior pituitary. This phase consists of following stages.
- Menstruation: Menstruation last for 2-8 days. The withdrawal of hormones (from ovary and endometrium) causes the shedding of superficial and intermediate layer of endometrium. The blood loss in menstruation is about 5-80 ml.
- Reparative stage: the repair of endometrium starts during menstruation. The blood vessels and glands in the Basal layers start to proliferate. This proliferation occurs under the influence of hormone i.e. OESTROGEN. The endomentim become thicker 3-4 mm but the secretory activity does not start in this phase.
This phase is of constant duration i.e. 14 days. The proliferative activity is continuous but the secretory activity is more dominant. This phase consist of following stages.
- Ovulation or O-Phase: The release of ovum from ovary, at 14th day of menstrual cycle, is called ovulation. At this time, there is a sudden increase in LH (Lutenizing hormones) from anterior pituitary gland which causes ovum to release.
- Corpus Lutenum or L-Phase: the endometrium now divides into 3 layes: Compact layer, Spongy layer, and Basal layer. During last 2-3 days of this phase, oedema of spongy layer disappears and blood vessels shrink and hemorrhagic areas appear. If fertilization occurs, the menstruation does not occur and the fertilized ovum starts to grow and takes nourishment from secretions of secretory phase. Then it enters into the Luteum phase of ovarian cycle. Corpus leutin lasts for 12 weeks.