Question

After the release of secondary oocyte from the Graafian follicle, the Graafian follicle turns into corpus luteum. In case of a successful pregnancy, the corpus luteum continues to function as an endocrine gland

• A. till the end of first week
• B. till the end of first two weeks
• C. till the end of first trimester
• D. throughout the gestation period

Answer 1

The correct option is C till the end of first trimester

After ovulation, i.e. the release of the secondary oocyte from the Graaffian follicle, the ruptured Graafian follicle turns into a structure called the corpus luteum. The corpus luteum functions as an endocrine gland and can release progesterone. But the viability of corpus luteum is dependent on whether there was a successful implantation or not. In case there was no implantation, the corpus luteum mostly degenerates within two weeks. But if there is a successful implantation, the corpus luteum can remain viable for first three months and secrete progesterone which helps in the maintenance of pregnancy. So, in case of successful implantation, the corpus luteum remains viable till the end of the first trimester.
It doesn’t remain viable throughout the entire gestational period because at the end of the first trimester, the placenta becomes fully functional and takes over the formation of progesterone. The corpus luteum is no longer required, hence it degenerates.