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Which one of the following is the most likely root cause why menstruation is not taking place in a regularly cycling human female?
A
Retention of well-developed corpus luteum
B
Fertilization of the ovum
C
Maintenance of the hypertrophied endometrial lining
D
Maintenance of high concentration of sex-hormones in the blood stream
Detailed Solution
Menstruation occurs only if the released ovum is not fertilised: the corpus luteum then degenerates, progesterone falls and the endometrium breaks down.
If the ovum is fertilised, the developing embryo and placenta produce hCG, which maintains the corpus luteum.
The corpus luteum continues to secrete progesterone, so the endometrial lining is maintained and menstruation stops; lack of menstruation may be indicative of pregnancy.
Thus the retention of the corpus luteum, the maintained endometrium and the high hormone levels are all consequences; their root cause is the fertilisation of the ovum.
Hence the most likely root cause is fertilisation of the ovum.
If the ovum is fertilised, the developing embryo and placenta produce hCG, which maintains the corpus luteum.
The corpus luteum continues to secrete progesterone, so the endometrial lining is maintained and menstruation stops; lack of menstruation may be indicative of pregnancy.
Thus the retention of the corpus luteum, the maintained endometrium and the high hormone levels are all consequences; their root cause is the fertilisation of the ovum.
Hence the most likely root cause is fertilisation of the ovum.