The Menstrual Cycle

The reproductive period in the female lasts about thirty years. During this time, her reproductive organs go through a cycle which is interrupted only by bearing a child. When a baby girl is born, her ovaries contain about 70,000 egg cells. These lie dormant until puberty. Then, driven by the anterior pituitary gland, the egg cells begin to ripen.

Egg Cell and Follicle

At about monthly intervals, an egg cell pushes its way to the surface of each ovary. As it does this, it is encased in a covering of special cells The developing egg in its cover is the Graafian follicle.

The Endometrium Prepares

As the follicle with its egg cell ripens, the ovary secretes oestrogen. This hormone, travelling in the blood to the womb, causes the lining, or endometrium, to' thicken and grow more blood vessels.

After about ten days, the follicle splits open, sending the egg cell down into the Fallopian tube. The follicle cell, empty of the egg, then makes another hormone, pro-gesterone. This stimulates the endometrium even more. It becomes very thick and spongy. Special food stores appear in the lining of the womb, together with many glands. The endometrium is thick, and full of blood and food ready to shelter and feed a tiny embryo.The egg meanwhile journeys down the Fallopian tube to the uterus.

The Fertilised Egg Settles

If it has been fertilised by a spermatozoon en route, the zygote quickly burrows into the endometrium. From the blood flowing so freely through the endometrium, the tiny embryo can take the oxygen and food it needs for survival. Eventually a special organ (the placenta) grows from the tissues of mother and embryo. The placenta allows the developing child, or foetus, to feed on the mother.

The Unfertilised Egg Dies

What is the fate of the unfertilised egg? It dies inside the womb. This happens to most egg cells. Only a few eggs are fertilised during the lifetime of one woman. After the egg has died, the ovary temporarily loses interest in the uterus.

The Womb Sheds its Lining. The hormones which were secreted in order to prepare the womb for an embryo are no longer formed. The growth of the endometrium is dependent on these hormones. As they wane in the blood, the lining of the womb changes very dramatically. Almost the whole thickness peels off arid is discarded. At this point, the monthly period begins. The discharge con-sists of blood and tissue shed from the wall of the uterus, tissue which was prepared for an embryo and which is no longer required.

The Cycle Repeats

The ovary produces ripe ova at approximately monthly intervals throughout the thirty years or so of a woman's reproductive life. Each time an egg cell leaves the ovary, the womb prepares to receive an embryo. If the egg remains un-fertilised, no embryo can develop, and so the lining of the womb is discarded. It is rebuilt as the next egg cell develops inside its follicle. The menstrual cycle is interrupted only when an embryo implants itself in the endometrium so carefully prepared for it. Then the ovary produces no more egg cells until the embryo (or faetus) has completely developed and a child is born. After the birth of the child the cycle begins again.

Changes in the Breasts

The ovarian hormones, progesterone and cestrogen, also affect the breasts, stimulating the glandular tissue. During each menstrual cycle, the breasts vary a little in size. They are usually largest just before the beginning of a period when there is most hormone in the blood.

Premenstrual Tension

The hormones have other actions, and probably cause the feeling of tiredness and anxiety-called premenstrual tension-which many women experience just before a period begins.

Pituitary Control

The ovary is awakened by the anterior pituitary gland at puberty. Throughout reproductive life the pituitary drives the ovary by means of the trophic hormones which it secretes. These make the ovary produce cestrogen and progesterone. The pituitary gland is, indirectly, responsible for the menstrual cycle. If the anterior pituitary is damaged, the menstrual cycle stops altogether. This of course makes child-bearing impossible.

The Menopause

Reproductive life ends at the menopause. For most women, this occurs in the forties.

Irregular Periods

The periods become irregular, and may be very scanty or ex-tremely heavy. The amount of bleeding at each period seems to depend on the balance of oestrogen and progesterone in the blood. If the normal balance is upset, bleeding may be very heavy. As the ovary fails, it secretes its hormones in a rather erratic manner. This interferes with the menstrual cycle, making it irregular, and causing the heavy periods.

Uterine Operation

Since it is the uterus which bleeds, heavy periods at the menopause can be stopped by removing the womb. This is a major operation, and is not desirable unless the bleeding is making the patient anaemic. It is not usually necessary, since the periods stop naturally when the ovary ceases to function altogether.

Hot Flashes

Menopausal women often feel emotionally upset. They have ‘hot flushes’ and other inconveniences which may be very disturbing. Some doctors think that these symptoms are caused by a change in the cestrogen secretion. They may often be relieved by small doses of oestrogen given for a short time. After the menopause the reproductive organs atrophy, and the woman usually grows fatter.

Male Climacteric

There is no such abrupt ending to the reproductive life of the male. His gonads may continue to produce healthy spermatozoa when he is in his sixties.

Dr. Sitara Rahman

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