Biology for IGCSE & O level - Reproduction (Section 4 - No. 39)
What event directly triggers the start of menstruation?
A surge of estrogen.
A surge of progesterone.
A decline in estrogen and progesterone levels.
The release of an egg from the ovary.
Explanation
A drop in estrogen and progesterone causes the uterine lining to shed, resulting in menstruation.
Comments (0)
