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If mammalian ovum fails to get fertilized, which one of the following is unlikely -
A
Estrogen secretion further decreases
B
Progesterone secretion rapidly declines
C
Corpus luteum will disintegrate
D
Primary follicle starts developing
Detailed Solution
If the ovum is not fertilised, the corpus luteum degenerates (disintegrates) towards the end of the luteal phase; this is likely.
With the degeneration of the corpus luteum, the secretion of progesterone declines rapidly; this is likely.
The corpus luteum also secretes oestrogen, so the oestrogen level falls further; this is likely. The fall of these hormones leads to menstruation.
Primary follicles are formed in the ovary during foetal life, and their numbers only decline afterwards; no new primary follicles are formed in the adult.
According to the answer key, the statement that a primary follicle starts developing is therefore the unlikely one; what begins in the next cycle under FSH is the growth of already existing follicles into Graafian follicles.
Note: some books treat the start of development of a new follicle as a normal event after failure of fertilisation, so this question is open to interpretation.
With the degeneration of the corpus luteum, the secretion of progesterone declines rapidly; this is likely.
The corpus luteum also secretes oestrogen, so the oestrogen level falls further; this is likely. The fall of these hormones leads to menstruation.
Primary follicles are formed in the ovary during foetal life, and their numbers only decline afterwards; no new primary follicles are formed in the adult.
According to the answer key, the statement that a primary follicle starts developing is therefore the unlikely one; what begins in the next cycle under FSH is the growth of already existing follicles into Graafian follicles.
Note: some books treat the start of development of a new follicle as a normal event after failure of fertilisation, so this question is open to interpretation.