Menstrual cycle:
- It is found only in primate females.
- Its duration is 28 to 30 days in the woman and 35 days in the chimpanzee.
- In woman, the menstrual cycle begins at an age of 12 years which is called menarche.
- The menstrual cycle ceases naturally at an age of 45 to 50 years which is called menopause.
The menstrual phase has 4 phases of viz.
1. Menstrual phase:
- Its duration is of 3 to 5 days in a woman.
- Term menstruation means bleeding.
- During this phase, the blood is released along with dead ovum & pieces of the uterine endometrium.
- The ovary has immature follicles & corpus Albicans.
- The body has less estrogen & the progesterone is almost absent.
2. Follicular phase or Proliferative phase:
- Its duration is of 8 to 10 days.
- Maximum estrogen in the blood.
- Formation of Graffian follicles up to the end of this phase.
- Increased thickness of the uterine wall and increased number of uterine B.Vs. & uterine glands.
- Blood FSH is increased but blood LH is reduced.
3. Ovulatory phase or recovery phase:
- There is ovulation which occurs 14th + 2 days in a woman.
- The ovary has burst Graffian follicle.
- FSH & Estrogen get lowered slightly.
4. Luteal phase or secretory phase:
- It is also called as the pre-menstrual phase.
- It is the longest phase. Its duration in a woman is 12 to 16 days.
- The ovary shows fully developed corpus luteum.
- Myomatrium & endomatrium are maximum developed.
- Maximum estrogen, progesterone & LH in the blood.
- Uterine glands are completely developed & corkscrew-shaped.
- The female remains in lateral phase till parturition.
- If there is no fertilization, the menstrual cycle is repeated.
- Increase in body temperature