Reproduction in Lower and Higher Animals — BIOLOGY STD 12 Science — Question
Maharashtra BoardEnglish MediumSTD 12 ScienceBIOLOGYReproduction in Lower and Higher Animals2 Marks
Question
Missing of menses is the first indication of pregnancy.
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Answer
Menstruation occurs if there is no fertilization of ovum.
The endometrium of uterus along with unfertilized egg is given out in the form of menstrual flow.
The sloughing off uterine endometrium takes place due to degeneration of corpus luteum.
In the absence of functional corpus luteum progesterone levels fall down. However, if the ovum is fertilized, the corpus luteum is maintained and it secretes progesterone which maintains the uterine endometrium. In such case, further growth of ovarian follicles and ovulation remains suspended and woman is said to be pregnant.
Endometrial wall of uterus now thickens and helps in the growth of placenta. Thus during pregnancy, menses will not take place.
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