The menstrual flow results due to:
(A) Increased estrogen levels
(B) When released ovum is not fertilized
(C) When pregnancy occurs
(D) Breakdown of the endometrial lining of the uterus and its blood vessels
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (B) and (D) only
(A) Increased estrogen levels — Incorrect. Menstruation follows a fall in the hormones, when the corpus luteum degenerates and progesterone drops. Rising estrogen belongs to the follicular phase, when the endometrium is being rebuilt.
(B) When released ovum is not fertilized — Correct. If the ovum is not fertilised, the corpus luteum degenerates and the endometrium is shed.
(C) When pregnancy occurs — Incorrect. During pregnancy all events of the menstrual cycle stop, and there is no menstruation. That is why a missed period may be a sign of pregnancy.
(D) Breakdown of the endometrial lining of the uterus and its blood vessels — Correct. This breakdown forms the liquid that comes out through the vagina as the menstrual flow.
NCERT Extract:
Menstrual Cycle – “… The cycle starts with the menstrual phase, when menstrual flow occurs and it lasts for 3-5 days. The menstrual flow results due to breakdown of endometrial lining of the uterus and its blood vessels which forms liquid that comes out through vagina. Menstruation only occurs if the released ovum is not fertilised.”