(i) The commencement of menstruation at puberty is termed menarche and marks the beginning of the reproductive life of a female.

(ii) Initially, inside the ovary, an oogonium or an ovarian follicle is developed into a mature ovum and released into the fallopian tube. This is termed as ovulation.

(iii) After the release, the uterus and the fallopian tubes undergo changes like the thickening of the uterine wall, development of the endometrial lining, etc. to prepare the body for a probable pregnancy.

(iv) If fertilization does not occur, then the thickened inner wall of the uterus breaks down along with its blood vessels and moves out of the vagina in the form of bleeding, called menstrual flow (menstruation).

(v) It lasts for about 4-7 days.

(vi) This cycle of events taking place in the ovaries and the uterus every 28 days and marked by the menstrual flow is known as the menstrual cycle.

(vii) In a normal healthy woman, ovulation takes place around the 14^th day and menstruation occurs every 28 to 30 days.