Question

Define menstrual cycle. Give an account on hormonal interplay during it.

Hint:

FSH = follicle growth, Estrogen = endometrium repair, LH surge = ovulation, Progesterone = endometrium maintenance.

Answer 1

Step 1: Definition.
The menstrual cycle is a series of cyclic changes occurring in the ovaries and uterus of females, usually lasting about 28 days, starting from the first day of menstruation. It prepares the female body for fertilization and pregnancy.

Step 2: Phases of menstrual cycle with hormonal control. \begin{enumerate} \item Menstrual phase (Day 1–5): \[\begin{array}{rl} \bullet & \text{Shedding of the uterine lining (endometrium).} \\ \bullet & \text{Caused by a sudden fall in progesterone and estrogen due to degeneration of corpus luteum.} \\ \end{array}\] \item Follicular/Proliferative phase (Day 6–14): \[\begin{array}{rl} \bullet & \text{Follicle Stimulating Hormone (FSH) from pituitary stimulates ovarian follicles to grow.} \\ \bullet & \text{Developing follicles secrete estrogen.} \\ \bullet & \text{Estrogen repairs and thickens the endometrium.} \\ \end{array}\] \item Ovulatory phase (Around Day 14): \[\begin{array}{rl} \bullet & \text{A surge in Luteinizing Hormone (LH) triggers ovulation (release of ovum from Graafian follicle).} \\ \end{array}\] \item Luteal/Secretory phase (Day 15–28): \[\begin{array}{rl} \bullet & \text{Corpus luteum forms from the ruptured follicle and secretes progesterone.} \\ \bullet & \text{Progesterone maintains the endometrium for possible implantation of embryo.} \\ \bullet & \text{If fertilization does not occur, corpus luteum degenerates, progesterone and estrogen levels drop, and menstruation starts again.} \\ \end{array}\] \end{enumerate}

Step 3: Significance.
The menstrual cycle ensures that the uterus is prepared every month for the implantation of a fertilized egg, making it essential for reproduction.