What is Menstruation? Explain.

What is menstruation ? What are the specific actions actions of FSH,LH, estrogens and progesterone in the menstrual cycle ?

(a) For how much time does menstruation last in females (or women) ? (b) What is the frequency of menstrual cuycle in human females (or women) ?

The first menstruation beings at ul((A)) and is called ul((B)) .