The Menstrual Cycle

Flow Phase

• Start of bleeding marks Day 1 of phase

• It is the shedding of the endometrium

• Occurs due to low hormone levels

Follicular Phase

• Occurs during day 6-13

• Period of repair and thickening of endometrium

• FSH from the pituitary promotes follicle development in the ovary

• As follicle develops, it produces estrogen

• FSH production decrease due to negative feedback from estrogen

• LH production increase due to GnRH

Ovulation Phase

• LH causes ovulation to occur on day 14

• Secondary oocyte is released from the follicle/ovary

Luteal Phase

• Final preparation if endometrium to receive the fertilized ovum

• LH stimulates development of corpus luteum

• Causes progesterone levels to increase

• If no fertilization, corpus luteum degenerates

• Estrogen & progesterone inhibit GnRH, thereby decreasing LH & FSH levels

• This low level of hormones initiates the flow phase