What is a menstrual cycle?

Menstruation is the cyclic discharge of unfertilized egg, debris, tissues from the uterus along with blood.

The menstrual cycle is of 28 days and can be divided into 4 phases on the basis of events occurring. Menstrual, follicular, ovulatory, and luteal are 4 phases.

• Menstrual phase: This occurs when fertilization of the egg doesn?t take place. As there is no fertilization and implantation of the egg, the uterine lining sheds.
• The bleeding lasts for 4-5 days. In this phase level of oestrogen and progesterone decrease.

• Proliferative / Follicular phase: In this phase follicles in the ovary matures. The mature ovum is ready for ovulation by the end of this phase.
• During this phase, the pituitary starts releasing FSH (Follicular stimulating hormone.

• Ovulatory phase: Mature ovum is released from the ovary. This occurs on the 14th day (+/- 1) of the cycle.
• Fertilization occurs at this stage of the cycle. In this phase, an increasing level of oestrogen triggers the release of luteinizing hormone (LH).

• Secretory/ Luteal phase: 
• In this phase- The fate of the corpus luteum is decided. If fertilization occurs ? it's maintained.
• If fertilization doesn?t occur then the corpus luteum has degenerated. In this phase, luteinizing hormone and follicle-stimulating hormone levels decline.
• The ruptured follicle seals after delivering the egg and develops a corpus luteum, which delivers progesterone. The oestrogen level is also high.