This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
True about estrogen production in menstural cycle? 
Select and explain. 
A. Only by theca cells, B. Only by granulosa cells, C. Both theca and granulosa cells, D. None of the above
C: Both theca and granulosa cells
Answer: C: Both theca and granulosa cells 
Explanation: Ans. is 'c' i.e., Both theca and granulosa cells Ovarian follicle contains two types of cells in preovulatory phase :-i) Granulosa cells :- Secrete mainly estrogen and very minimal amount of progesterone.ii) Theca cells (interna & externa) Theca interna cells provide androgen and pregnenolone to granulosa cells to conve them into estrogen and progesterone respectively.After ovulation, corpus luteum contain two types of cell :-i) Granulosa luteal cells (formed by luteinization of granulosa cells) :- Produce mainly estrogen and minimal progesterone.ii) Theca luteal cells (formed by luteinization of theca interna cells) :- Produce mainly progesterone.