Question

Describe the events that occur during secretory phases of the menstrual cycle.

Answer 1

Secretory Phase (lasts from about the 15th to 28th day of the menstrual cycle):

• After ovulation, the ruptured follicle transforms into the corpus luteum.
• The corpus luteum secretes large amounts of progesterone (and some estrogens).
• Progesterone causes the endometrium of the uterus to become highly vascularized, glandular, soft, moist, and thick, preparing it to receive and nourish a fertilized egg.
• Uterine glands secrete nutrient-rich mucus (often called uterine milk) to nourish the dividing embryo.
• The uterus is thus ready for implantation of the fertilized egg.
• If fertilization does not occur, the corpus luteum degenerates into corpus albicans, progesterone levels fall, and the endometrium degenerates, leading to menstruation and the start of a new cycle.