Question

Why does menstruation occur?
A. Shredding blood
B. Shredding endometrium lining and mucous
C. Shredding of ovum
D. None of these

Answer 1

One of the phases of the menstrual cycle is menstruation. Then blood came through the cervix and out through the vagina. The process usually takes three to five days. The quantity of menstrual blood varies from time to time and from one woman to another.

Complete answer:
Let’s first of all we study about menstruation.
In human women, the reproductive phase is $30 - 33$ years. This begins with puberty and ends with menopause.
During this phase, the reproductive tract and ovaries undergo cyclical changes that aim to fertilize the reproductive tract and prepare it to receive a fertilized egg. This cyclical process is known as the menstrual cycle. The most prominent activity of this phase is vaginal bleeding known as menstruation.
This menstrual cycle lasts an average of $28$ days, but it can vary from individual to individual.
The menstrual cycle is divided into four phases:
-Menstrual phase
- Proliferative Phase
-Ovulatory Phase
-luteal phase
Women's reproductive years are marked by the beginning and end of the menstrual cycle. The first menstrual period usually occurs around age $12$ or $13$, an event known as menarche. Termination of a woman's menstrual cycle at the end of a woman's reproductive year is known as menopause.
Menstrual phase-It lasts from day $1$ to day $4$ of the menstrual cycle and lasts $3 - 4$ days. If fertilization of egg doesn’t occur the corpus luteum starts to degenerate.
The level of progesterone in the blood decreases. Therefore, uterine tissue cannot be preserved. An unfertilized egg with a crushed uterine lining (endometrium), a portion of the mucous membrane and $50 - 100$ ml of blood is removed through the vaginal opening and is called menstrual flow or menstruation.
So, the correct answer is “Option B”.

Note:
When the levels of oestrogen and progesterone in the blood decrease, this stimulates the hypothalamus and the front of the pituitary gland to secrete FSH-RF and FSH, respectively. FSH starts the follicular phase of the next menstrual cycle. This is known as positive feedback.
Menstrual cycles do not exist during pregnancy, may not occur during breastfeeding, and completely stop at menopause.