We will now describe the sexual cycle in human females (or women). Please note that when a girl child is born, her ovaries already contain many thousands of immature ova (or eggs) which are contained in immature follicles.

When a girl reaches the age of puberty, then one follicle develops at a time to form a mature ovum (or egg). On maturing, the follicle bursts and the ovum (or egg) shoots out of the ovary. This is called ovulation. Thus, the release of an ovum (or egg) from an ovary is called ovulation.

In a normal, healthy girl (or woman), ovulation takes place on the 14th day of the beginning of menstrual cycle of 28 days. This means that ovulation takes place in the middle of the menstrual cycle (because 14th day is the middle of 28 days).

In human females (or girls), the ovaries start releasing ovum or egg (female gamete) once every 28 days from the age of puberty. That is, in girls ovulation starts when they attain puberty. Please note that ovulation does not take place every day after puberty. It takes place after a period of every 28 days (which is almost once a month).


Before every ovulation, the inner lining of the uterus becomes thick and soft with lot of blood capillaries (or blood vessels) in it. These changes in the uterus are necessary because in case the ovum (or egg) released by the ovary gets fertilised by the sperm, then the uterus has to keep this fertilised ovum (or egg) for further development and supply it with food and oxygen, etc., so that it may grow into a baby in due course of time.

If, however, a sperm is not available at the time of ovulation, then fertilisation of ovum (or egg) does not take place. Since the ovum (or egg) is not fertilised, so the thick and soft uterus lining having lot of blood capillaries in it is not required.

Thus, the unfertilised ovum (or egg) dies within a day and the uterus lining also breaks down. Since the thick and soft uterus lining contains a lot of blood vessels, so the breaking (or disintegration) of the uterus lining produces blood along with other tissues. This blood and other tissues come out of the vagina in the form of ‘bleeding’.

We can now say that the breakdown and removal of the inner, thick and soft lining of the uterus along with its blood vessels in the form of vaginal bleeding is called menstrual flow or menstruation.


Menstruation occurs if an ovum (or egg) released by the ovary of a woman does not get fertilised due to non-availability of sperm at the time of ovulation. Since the process of menstruation in a woman occurs again and again after a fixed period of 28 days (to 30 days), so it is also known as menstrual cycle.

Menstruation occurs every 28 days because ovulation (release of ovum or egg by ovary) occurs every 28 days. In everyday language, menstruation is called ‘periods’. We will now describe the menstruation (or menstrual cycle) point-wise which can be reproduced in the examination.

The sexual cycle in females (or women) is called menstruation or menstrual cycle. This is described below:

1. When a girl reaches puberty at the age of about 10 to 12 years, the sex hormones released into her blood cause some of the ova (or egg cells) in her ovaries to become mature (or ripe).


2. Usually one mature ovum (or egg) is released from the ovary into the oviduct once every 28 days. This is called ovulation.

3. Before ovulation (or release of ovum), the inner lining of uterus becomes thick and spongy, and full of tiny blood vessels (or blood capillaries), and prepares itself to receive the fertilised ovum or egg (in case it gets fertilised by sperm).

4. If the ovum (or egg) does not get fertilised (due to non-availability of sperm in the female body) then the thick and soft inner lining of uterus is no longer needed and hence it breaks. So, the thick and soft inner lining of uterus along with the blood vessels and the dead ovum (or egg) comes out of the vagina in the form of a bleeding called menstruation.

5. Menstruation usually occurs 14 days after ovulation and usually lasts for about 3 to 5 days.


6. After menstruation is over, the inner lining of the uterus starts building up again so that it may become ready to receive the next ovum (or egg) in case it gets fertilised.

7. If the ovum (or egg) does not get fertilised even now, then menstruation takes place again. This cycle of menstruation is repeated again and again in women after every 28 days (till the time ovum gets fertilised). The menstrual cycle is controlled by hormones.

Menstruation stops temporarily when the ovum (or egg) gets fertilised and the woman gets pregnant. This is because in this case the thick and soft lining of the uterus containing lot of blood vessels is needed for the growth and development of the fertilised ovum (or fertilised egg cell) to form a baby. Menstruation restarts after the birth of the baby.