Menstruation cycle:

 

• The reproductive cycle in the female primates (e.g. monkeys, apes and human beings) is called menstrual cycle. In human females, menstruation is repeated at an average interval of about 28/29 days, and the cycle of events starting from one menstruation till the next one is called the menstrual cycle.
• The first menstruation begins at puberty and is called menarche.
•  In human beings, menstrual cycles stops around 50 years of age, it is termed as menopause.

Menstruation cycle completes in 4 steps:

1) Menstruation phase: Lasts for 3 days.

i)The soft tissue of endometrial lining of uterus breaks and causes bleeding.

ii) The unfertilized egg and breaked tissue along with blood, keep on its flow outside of female body.

2) Follicular phase (Proliferative phase): Lasts for 10 to 14 days.

i) Endometrium starts regenerating due to increase in secretion of LH and FSH and also estrogen.

ii) Primary follicle matures into mature graffian follicle.

3) Ovulatory phase: Lasts for 2 days.

i) High increase in flow of LH and FSH breaks graffian follicle and secretes ovum (egg) called ovulation.

4) Luteal phase (Secretory phase): Lasts for 1day.

i) If pregnancy occurs then ruptured graffian follicle becomes corpus luteum in ovary, which secretes progesterone. This progesterone thickens the endometrium suitable for foetus and for pregnant mother to bear the surviving foetus in her womb.

ii) If pregnancy does not occur then graffian follicle degenerate and endometrium starts degenerating.