The ovaries resemble large almonds in shape and size, and are situated one each side of the uterus just below the fimbriated end of the Fallopian tube. They are therefore quite close to the sidewall of the pelvis and are protected from damage by the bones which form the pelvic girdle. They are extremely tender if pressure is exerted upon them. In a young girl, the surface is smooth and pink, but later it becomes grey and rather puckered due to the formation of repeated tiny scars which are caused by the process of ovulation. After the menopause when there are no more ova remaining, the ovary becomes small, rather shriveled and wrinkled. The ovaries have two main functions; the production of hormones and the production of ova.
Production of hormones
The formation or the production of hormones from the ovary is vital to female throughout her reproductive life. The ovary produces two hormones, estrogen and progesterone.
The production of estrogen commences relatively early in life and it is responsible for the development and the maintenance of all the secondary sex characteristics, such as the breasts and body contour as well as the maturation of the vulva and the growth of the vagina, uterus and Fallopian tubes. Estrogen is also partly responsible for the regulation of the menstrual cycle. At the time of the menopause when the ovaries cease to produce the required amount of estrogen, the periods stop and symptoms of the menopause develop. If the level of the estrogen falls very low, postmenopausal symptoms develop.
Progesterone is produced from the corpus luteum, which is the small gland that forms in the ovary after ovulation has occurred. This hormone is essential for the maintenance of pregnancy and also for the development of many symptoms during early pregnancy. It is also responsible for ripening the endometrium, or lining of the uterus, during the second half of the menstrual cycle, and is one of the major factors responsible for a regular menstrual period as well as a normal menstrual flow.
The functioning of the ovary is under the direct control and command of the pituitary gland. This is small gland situated in the base of the brain and is responsible for controlling most of the glandular secretions throughout the entire body. It not only controls the normal menstrual cycle but is also responsible for the onset, rhythm and eventual cessation of menstruation. The pituitary produces a small amount of an extremely powerful hormone called follicle-stimulating hormone (FSH) which is released into the blood stream and circulates to the ovary, within which it provokes the formation of follicles. The developing follicles manufacture estrogen. One of the follicles ripens and bursts liberating an ovum - ovulation. This process is induced by FSH. Another pituitary hormone, called luteinizing hormone (LH), also reaches the ovary via the blood stream to cause ovulation and forms the corpus luteum which can then secrete progesterone.
When fertilization occurs, the body has to take firm action to prevent another ovum being released and the next menstrual period occurring. The fertilized ovum embeds within the endometrium seven days after ovulation. This is accomplished by the chorionic villi that surround the fertilized ovum and have the ability to erode maternal tissue. The chronic villi produce a hormone known as chorionic gonadotropin which reaches the ovary by way of the maternal bloodstream forcing it to produce more progesterone which, in turn, will suppress the pituitary gland secretion of follicle-stimulating hormone. The net result is that the corpus luteum continues to increases in size, thus increasing the amount of progesterone secreted, while the suppression of the production of follicle-stimulating hormone means that no more follicles ripen in the ovaries.
If fertilization does not occur, the corpus luteum begins to shrivel on about the 26th day of the cycle. The consequent fall in progesterone as well as in estrogen level results in menstruation. If, however, fertilization has occurred then the production of chorionic gonadotropin from the chorionic villi results in a dramatic increase in secretion of progesterone from the ovarian corpus luteum which rapidly enlarges. The enormous increase in progesterone production together with its prolonged secretion beyond the 26th day of the menstrual cycle means the menstruation does not occur. The endometrium within the uterus remains intact and the newly implanted pregnancy is allowed to continue growing. Progesterone not only creates the secretory changes in the lining of the uterus, which are essential for the nutrition of the new pregnancy, but it also causes softening and relaxation of the uterine muscle as well as other involuntary muscle throughout the body, especially in the intestine, the bladder and blood vessels. It does not affect the heart itself. Relaxation of the muscle in the walls of many of the blood vessels occasionally results in a fall in blood pressure, especially when a pregnant woman is standing, and this predisposes her to fainting attacks. Relaxation of the muscular wall of the intestine predisposes to constipation, which together with relaxation of the muscular wall of the blood vessels round the anal canal may result in the formation of hemorrhoids or piles. Slackening and relaxation of the muscle wall of the bladder and of the muscle in the wall of the uterus that connect the kidneys to the bladder predispose the pregnant woman to infections in the urinary tract. Progesterone is also responsible for the increase in the size of the breasts during early pregnancy, as well as the nausea, which affects most women.
The ovary of the newborn female infant contains all the ova which she is likely to need during her life (together with many more besides). These are formed while the female baby is still in the uterus, and can be damaged during their development. While x-rays will not damage the baby itself, it is known that they can affect or damage the genetic pattern of the chromosomes within the developing ova of the baby. Pregnant women are therefore x-rayed as little as possible. Intensive x-ray investigations are not advisable because of the possibility that the child may develop leukemia or that future generations may be adversely affected.
