4. The figure below shows changes that take place during menstrual cycle in human. MENTRUAL CYCLE a) Name the hormones whose concentrations aro represented by curves B and D . (2 marks) B D b) Name the organs where the secretion of the following hormones occurs (2 marks) A C c) State the effects of the hormones C and D on the lining of the uterus. (2 marks) C D

a) The hormones whose concentrations are represented by curves B and D are estrogen (B) and progesterone (D).<br /><br />b) The organs where the secretion of the following hormones occurs are:<br />- Estrogen (B): Ovaries<br />- Progesterone (D): Corpus luteum in the ovaries<br /><br />c) The effects of the hormones C and D on the lining of the uterus are:<br />- Estrogen (C): Stimulates the growth and thickening of the uterine lining (endometrium).<br />- Progesterone (D): Maintains and further thickens the uterine lining in preparation for potential implantation of a fertilized egg.<br /><br />d) The fertile period during the menstrual cycle is typically around the time of ovulation, which is when the egg is released from the ovary. This usually occurs around the middle of the menstrual cycle, approximately 12-16 days before the start of the next menstrual period.