In: Anatomy and Physiology
Answer:- Female Menstrual cycle marks the reproductive period of a woman's life. Menstruation normally begins at the age of 12-15 years. The beginning of menstrual cycle is known as Menarche. The mentrual cycle ceases permanently at the age of 45-50 years. This is called as Menopause. The period between menarche and menopause is the fertile period of a female.
During the fertile period, cyclic events take place in the body every month. Normally ,the duration of menstrual cycle is 28 days. But variations are also seen in different females ranging from 20 to 40 days.
During the menstrual cycle, the body undergoes several changes. These changes take place in the ovaries, uterus,cervix and vag!na.
Changes in ovaries occur in the Follicular Phase and Luteal phase. The sequence of phases is as follows:
Follicular phase------ ovulation ---------- luteal phase.
1.Follicular phase- It commences from the 5th day of the menstrual cycle to the day of ovulation. This phase is marked by the growth and maturation of ovum.
2. Ovulation- it normally takes place on the14th day of menstrual cycle .
3. Luteal phase- this phase occurs from the 15th to 28th day of menstrual cycle. This phase is marked by the development of corpus luteum. The fate of corpus luteum is decided in this phase.
During ovulation, the ovum are released from the ovary. The ovum which was earlier a primary oocyte divides and becomes secondary oocyte + first polar body. The first polar body degenerates. The secondary oocyte ( ovum) is released from the ovaries and reaches the fallopian tube .
There are higher chances of fertilisation during this period i.e 14-17th day of menstrual cycle. If during this period ,there is ejaculation of semen in the vag!na,200-300 millions of sperms travel from vag!na to the fallopian tube. But among all of them,only one succeeds in fertilising the ovum.