In which phase does the corpus luteum form?

• A. Luteal Phase
• B. Follicular Phase
• C. Proliferative Phase
• D. Menstrual Phase

Answer: (A)

The corpus luteum forms after ovulation, during the luteal phase. When the mature follicle releases the oocyte, LH stimulates the ruptured follicle to transform into the corpus luteum. This structure then secretes progesterone (along with some estrogen) to prepare and maintain the endometrium for a possible pregnancy. If fertilization doesn’t occur, the corpus luteum regresses, progesterone falls, and menstruation begins. The follicular phase precedes ovulation, and the menstrual and proliferative phases relate to endometrial changes before and during early follicular activity.