Describe the regulation of the ovarian and uterine cycles. Include all stages of each cycle in your answer

Question

What will be an ideal response?

Answer 1

The ovarian cycle is under the influence of a variety of hormones. At the beginning of the cycle, FSH and LH from the pituitary gland stimulate oocyte development and follicle growth in the ovary; this is the follicular phase of the ovarian cycle. Estrogen secreted from the growing follicle also stimulates follicle growth and causes thickening of the endometrial lining; this is the proliferative phase of the uterine cycle. Elevated estrogen levels in the blood begin to inhibit FSH release from the pituitary, but LH levels continue to rise. About halfway through the cycle LH levels surge, causing the ovarian follicle to rupture and release a secondary oocyte. The ruptured follicle differentiates to form a corpus luteum that secretes progesterone; this begins the luteal phase of the ovarian cycle. Progesterone causes extensive thickening of the endometrial lining; this is the secretory phase of the uterine cycle. By about day 22, if fertilization does not occur the corpus luteum begins to degenerate and progesterone levels begin to decline. Around day 28 the endometrial lining detaches and menstruation begins; this is the menstrual phase of the uterine cycle. Low levels of estrogen and progesterone during this phase allow the pituitary to secrete more FSH and LH, and the cycles for the ovary and uterus repeat.