Question

Describe the hormonal changes and the process of ovulation during the menstrual cycle.

Answer 1

• The menstrual cycle is the cycle of events occurring in females, with monthly periodic blood discharge from the vagina due to the breakdown of the endometrial lining of the uterus.
  
• The cycle begins with the discharge of blood, i.e, menstruation, the shedding of the endometrial wall lining the uterus in case no fertilisation occurs.
  
• After this, anterior pituitary releases FSH and LH that stimulate the release of follicles from the ovary and develop it as mature egg for fertilisation. This also causes the ovary to release estrogen. FSH, LH and estrogen have positive feedback effect and increases the release of more FSH, LH and estrogen.
  
• Estrogen promotes the mucus and lining of the uterus to grow thicker to support the embryo.
  
• The surge of LH on about 14th day causes ovulation, the mature eggs come down into fallopian tube for fertilisation.
  
• The mature follicle develops into corpus luteum that start releasing progesterone and lowers the level of estrogen.
  
• Progesterone maintains the uterus lining and develops new blood vessels to support the developing embryo.
  
• Combine effect of the progesterone and estrogen have negative feedback and stops the release of FSH and LH.
  
• If ovum gets fertilised, progesterone continues to maintain the pregnancy, and if, ovum doesn't get fertilised, corpus luteum stops releasing progesterone and causes the uterine lining to shrink and shed the blood through menstruation and further increases the level of FSH and LH to repeat the cycle.