Question

Describe menstrual cycle in detail.
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Answer 1

Explanation:

The menstrual cycle is the regular natural change that occurs in the female reproductive system (specifically the uterus and ovaries) that makes pregnancy possible. The cycle is required for the production of oocytes, and for the preparation of the uterus for pregnancy.

Answer 2

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The endometrium of uterus thickens every month and is supplied with blood to nourish the embryo. It undergoes cyclic changes during the menstrual cycle.

There are four main phases in the menstrual cycle, they are :-

• Menstruation

• Follicular phase

• Ovulation

• Luteal phase

Menstruation : It is the removal of the thickened lining layer (endometrium) of the uterus from the body.The menstrual fluid contains the blood, endometrial cell and mucus. This phase extends for 3-5 days. The first occurrence of the menstruation is known as the menarche and the ending is called the menopause. 

Follicular phase : The pituitary gland releases the follicle stimulating hormone(FSH) which stimulates the ovary to produce follicle. Only one follicle mature to an egg, the follicle is known as the Graafian follicle.The outer layer of this follicle produces the oestrogen hormone.The oestrogen hormone build the lining of the uterus and stimulate or prepare it for pregnancy.This phase extends for 1-10 days. 

Ovulation : The increased level of FSH is during the follicular phase is recognised by the hypothalamus. So it releases a chemical called gonadotrophin-releasing hormone(GnRH).This GnRH prompts pituitary gland to produces a hormone called the luteinizing hormone (LH) when the follicle mature. This LH stimulates the rupturing of follicle and egg is released which is known as the ovulation. This phase extends for 10-16 days. The egg moves through fallopian tube to the uterus.

Luteal phase : The ruptured follicle aggregates to form  the corpus luteum. It then starts producing the oestrogen and progesterone hormones. These hormones helps in thickening the walls of the uterus. If the egg is fertilised, it implants in the lining of the uterus. The corpus luteum maintains high level of progesterone to maintain the thick lining of the uterus.

If the egg is not fertilised the corpus luteum dies off. The decreased level of progesterone causes the rupturing of the thickened lining layer (endometrium) of the uterus known as menstruation. There by repeating the cycle. 

Hope it helps !