The ovaries are a pair of ovum-producing glands that are part of the female reproductive system. Each ovary is oval shaped and roughly the size of an almond. They sit just above the fallopian tubes in the lateral wall of the pelvis in an area called the ovarian fossa. Each ovary is attached to the fimbria of the fallopian tube.
There are two extremities to the ovary called the tubal extremity (the end that attaches to the uterine tube) and the uterine extremity (the end that attaches to the uterus by the ovarian ligament).
The ovaries have two distinct functions. They produce ova (also called eggs) and they produce female hormones.
Every month during ovulation either the right or left ovary will produce a single mature eggs for fertilization. Even though only one egg will be fully mature during the ovulation period, there are approximately ten to twenty follicles (ovarian follicles are made up of a hollow ball of cells that contain an n immature egg in the center) that begin the process of maturation every month, with any excess follicles being reabsorbed before ovulation occurs.
After the ovary releases an egg it then begins its journey to the oviducts where it travels for several days into the uterus. The egg moves along through the fallopian tubes by wavelike muscle contractions within the fallopian tube. The fallopian tubes are lined interiorly with cilia that help move the sperm towards the egg if a woman has had unprotected intercourse. The fertilization of an egg with sperm usually occurs in the fallopian tubes nearest the ovary. It then takes another five to six days for the fertilized egg to reach the uterus.
The main source of the female hormones estrogen and progesterone come from the ovaries. These hormones are responsible for controlling the development of the female body characteristics including, breast size, and body shape.
The whole process of ovulation begins with, and is controlled by, a drop in the level of a hormone called estrogen. When the estrogen level drops the hypothalamus is sent a signal to increase its secretion of gonadotropin-releasing hormone which then sends a message to the pituitary gland to increase its secretion of follicle-stimulating hormone. This increase of the follicle-stimulating hormone is responsible for the growth of ten to twenty ovarian follicles. Estrogen is also secreted by some of the cells into the follicle. In addition, estrogen controls the growth of the uterine lining during the first phase of the menstrual cycle, and regulates various metabolic processes.
Another hormone called progesterone is also produced by the cells in the ovarian follicles. This occurs just before ovulation occurs. If pregnancy has not occurred, after ovulation the empty follicle (called the corpus luteum) is then reabsorbed into the body. These unfertilized eggs then either disintegrate or flow out of the body unnoticeably with vaginal secretions. If on the other hand, pregnancy does occur the follicle produces hormones that will help to sustain the pregnancy.