OVARIES

The ovaries not only produce and release eggs that are ready for fertilization. Their other vital role is to produce hormones that maintain the menstrual cycle and give a woman’s body its feminine shape.

The ovaries are the parts of the female productive system, which are designed to make a release mature ova or egg cells. When a sperm from a man fertilizes the ovum it marks the start of a new human life. From the first period to the menopause, normal ovaries release one egg each month. They are also essential parts of the body’s hormonal, or a endocrine system.

LOCATION AND STRUCTURE

The ovaries are two grey-pink, almond-shaped structures each about 1 cm (4 in) thick. They are found in the pelvis, the body cavity bounded by the hip or pelvic bones, and lie on each side of the uterus. Each ovary is held in place by strong, elastic ligaments just above each ovary is the feathery opening of the fallopian tube which leads to the womb, or uterus. Although they are very close to each other there is no direct connection between the ovary and the tube opening.

In a mature woman the ovaries have a rather lumpy appearance. The reason for this can be seen by looking at the internal structure under a microscope. Covering the ovary is a layer of cells called the germinal epithelium. It is from the cells in this border layer that the eggs or ova form; thousands of immature eggs, each in a round casing or follicle (the egg sac) can be seen clustered near the ovary edge.

Much more noticeable however are the follicles containing eggs in various stages of maturation. As these follicles enlarge, and after their eggs have been released, they produce the characteristic bumps on the ovary surface. The centre of the ovary is filled with elastic fibrous tissue which acts as a support for the follicle-containing outer layer.

OVULATION

Under a microscope, maturing follicles of the ovary can be seen as tiny balls enclosing a small mound of cells. In the centre of the mound is the egg cell in its final stages of maturation. When the follicle is ripe and the ovum mature, the cells at the follicle edge allow the ovum to leave. Exactly how this happens is still a mystery. The ovum is then wafted by the feathery ends, or fibria, of the Fallopian tubes into the tube openings.

In their role as egg producers the ovaries also act as hormonal or endocrine glands. The ovaries function under the control of the pituitary gland at the base of the brain. The pituitary first makes a hormone called follicle stimulating hormone (FSH) which travels in the bloodstream to the ovaries. FSH stimulates follicles and ovum development but it also brings about the secretion of the hormone oestrogen. Under oestrogen influence the lining of the uterus thickens in preparation for receiving a fertilized egg. Oestrogen also stimulated the build up of body proteins and leads to fluid retention.

After a follicle has ripened and burst another pituitary hormone, luteinizing hormone, or LH, goes into action and brings about the development of the corpus luteum in the empty follicle. (The job of corpus luteum is to help establish a pregnancy). In turn, the corpus luteum makes and release its own hormone, progesterone. If the egg is not fertilized within a fortnight the corpus luteum shrinks, progesterone production is turned off, and the lining of the uterus is shed as the monthly menstrual period. Now FSH production begins against and the whole cycle is repeated. If, however, the egg has been fertilized, then the corpus luteum goes on working until the placenta is established and there is no bleeding.

OVARY DEVELOPMENT

Ovary development is largely complete by the time the female is in the third month of life in the womb, and few major changes will take place until puberty. By the time a baby girl is born her ovaries contain, between them, from 40,000 to 30,000 primary follicles, each containing an immature egg. At most only 500 or so of these eggs will ever be released, and probably no more than half a dozen - if that -will develop into new human beings.

When the ovaries first start to make the hormone oestrogen, they are not yet capable of releasing mature eggs. these early oestrogens bring about the physical changes of puberty such as growth of breasts, widening of hips and pubic hair. These changes begin at least a year before a girl has her first period, and are a sign that the oestrogens have begun to stimulate the release of mature eggs.

WHAT CAN GO WRONG ?

Apart from the normal failure of the ovaries at menopause, the most common problem of the ovaries is the formation of ovarian cysts. These growths, which are usually benign, may grow to such vast proportions that they make a woman’s abdomen swell up as if she were pregnant. Many small ovarian cysts often disappear of their own accord and cysts usually cause pain only when they become twisted within the ovary.

EXAMINING THE OVARIES

From the outside of the body, the only way a doctor can examine the ovaries is by feeling, or palpating them.

For a more thorough internal examination a technique called laparoscope's is used. Under a general anesthetic, carbon dioxide gas is injected into the pelvic cavity. This makes the intestines move away from their normal position, so that they no longer obscure the ovaries. A tubular instrument, the laparoscope's, is inserted through or near the navel. The surgeon can then look directly at the ovaries and if he wishes take a tissue sample or biopsy.