Menstrual cycle
Read the following passage carefully and answer the given questions.
The reproductive cycle in the female primates is called menstrual cycle. The first menstruation begins at puberty and is called menarche. The cyclical changes in the ovary and the uterus during menstrual cycle are induced by changes in the levels of pituitary and ovarian hormones. One ovum is released during the middle of each menstrual cycle. The cycle starts with the menstrual phase, when menstrual flow occurs and it lasts for 3-5 days. Menstruation only occurs if the released ovum is not fertilised. Lack of menstruation may be indicative of pregnancy. The menstrual phase is followed by the follicular phase. During this phase, the primary follicles in the ovary grow to become a fully mature Graafian follicle and simultaneously the endometrium of uterus regenerates through proliferation. The secretion of gonadotropins increases gradually during the follicular phase, and stimulates follicular development as well as secretion of estrogens by the growing follicles. Both LH and FSH attain a peak level in the middle of cycle. Rapid secretion of LH leading to its maximum level during the mid-cycle called LH surge which induces rupture of Graafian follicle and thereby the release of ovum. The ovulation is followed by the luteal phase.
In reproductive cycle, menstrual fluid is released due to:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Breakdown of endometrial lining
The passage says that menstruation occurs only if the released ovum is not fertilised. In the absence of fertilisation, the corpus luteum breaks down and progesterone falls. Without progesterone, the endometrium cannot be maintained. The menstrual flow results from the breakdown of the endometrial lining of the uterus and its blood vessels. This forms a liquid that comes out through the vagina.
(1) Breakdown of endometrial lining — Correct. The broken-down uterine lining and its blood vessels make up the menstrual fluid.
(2) Ovulation — Incorrect. Ovulation is the release of the ovum in the middle of the cycle. It does not produce any fluid.
(3) LH secretion — Incorrect. LH (luteinising hormone) is a gonadotropin of the anterior pituitary. The LH surge in mid-cycle causes ovulation, not menstruation.
(4) Menopause — Incorrect. Menopause is the end of menstrual cycles around 50 years of age.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Menstrual Cycle – …
