When a woman is fertile, each month a Graafian follicle travels to the surface of the ovary, bursts, and releases an egg and its fluid contents into a fallopian tube. Also within the ovaries are small numbers of corpus lutea - the remains of Graafian follicles that have released an egg and are in the process of being reabsorbed by ovarian tissue. Progesterone is the pregnancy hormone that readies the lining of the uterus for the arrival of a fertilized egg. During the first half of a woman's menstrual cycle - about 2 weeks before ovulation, an egg is released. When the blood-borne FSH reaches the ovaries, it spurs the Graafian follicles to grow and produce estrogen.
Additional estrogen is made by hormone-producing tissue within the stroma.
One Graafian follicle in an ovary begins to outgrow the other follicles while the estrogen level is increasing. The LH causes the Graafian follicle to bubble out on the outside of the ovary, burst, and eject its egg into the fallopian tube. This process of ovulation occurs on or about the 14th day of the menstrual cycle. The ovulated egg travels through the fallopian tube for 5 to 7 days, after which it is released into the uterus. The ovaries are held in place by bands of fibrous tissue known as ligaments.