Why does menstruation occur? Describe the menstrual cycle in human females (or women).

In female, ovary produces one egg every month. The uterus also prepares itself to receive a fertilised egg. So, the wall of uterus becomes thick and soft containing lots of blood capillaries. If egg gets fertilised with sperm, then fertilised egg gets attached with uterus wall and gets nourishment from it. In case, egg is not fertilised, then the inner lining of uterus breaks down and comes out in the form of blood and mucus through the vagina. This cycle occurs every month and is called menstruation.

Menstrual Cycle:


(i) Menstrual cycle begins when a girl reaches the age of puberty. At this age, ovaries release sex hormones in the blood which cause maturation of ova in ovaries.


(ii) One mature egg is released from the ovary into fallopian tube. This is termed as ovulation.


(iii) Before ovulation, uterus prepares itself to receive the fertilised egg. The inner linning of the uterus becomes thick and soft with lots of blood capillaries in it.


(iv) If the ovum does not get fertilised, then the inner lining of uterus is not required and hence it breaks down and comes out through the vagina in the form of blooding called menstruation.


(v) Menstruation usually lasts for 3 to 5 days.


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


(vii) If the ovum does not get fertilised even now, then the menstruation takes place again and this cycle goes on repeating.


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