THE FEMALE SEX GLANDS
The sex glands, or gonads
The gonads—from the Creek word gonos, meaning seed—consist of the testicles in men and the ovaries in women. Besides producing sperm and egg cells, the sex glands make the hormones that are responsible for the special characteristics of the male and female.
The female sex glands
The female sex glands are called the ovaries. Like the testicles, there are two of them. Besides producing eggs, the ovaries secrete hormones necessary for feminine characteristics and for reproduction.
The hormones produced by the ovaries are the oestrogens and progesterone. There is very little secretion of them before puberty and after the menopause. They are produced abundantly, however, during a woman’s childbearing years.
Menstruation is the periodic discharge from the body of the extra blood and tissue that have built up in preparation for a baby and have not been used. Although menstrual cycles vary, the time from one menstrual period to the next is usually about 28 days.
Doctors customarily count the first day of menstruation as Day I. During the first 14 days of the cycle, the ovary contains the Graafian follicle—a small hollow ball the size of a pinhead. Within it lies an egg. This follicle grows during these 14 days until it is several times its original size, becoming as large as a pea. While it is growing, the follicle makes the oestrogen hormones. The menstrual cycle and the growth of the follicle are under the control of the pituitary gland.
On about Day 14, stimulated by the pituitary gland, the follicle bursts and the egg enters the Fallopian tube on its way down to the uterus. If any sperm cells are present in the tube at this time, fertilization may take place. The fertilized egg continues its journey down the tube and plants itself in the wall of the uterus. Meanwhile, the ruptured follicle from which the egg was discharged is transformed into a yellowish, solid ball called the corpus luteum (Latin for yellow body). This body produces another hormone, progesterone.
Scientists have learnt how to make synthetic hormones in the laboratory, so that the process of ovulation can be controlled at will. The contraceptive pill imitates the natural body processes in preventing ovulation.
Oestrogens as well as progesterone play two important roles in the female body. They are largely responsible for the development of feminine characteristics; and they influence the building up of the lining of the uterus in preparation for receiving and nourishing the fertilized egg. During the last 14 days of the cycle, the hormones produced by the corpus luteum stimulate the manufacture of the tissues and blood supply in the uterus.
The fertilized egg in turn secretes its own hormone. This hormone helps the corpus luteum to persist and continue making oestrogen and progesterone. In other words, it is like a chain reaction, with one hormone prodding the other two hormones to keep going.
If pregnancy does not occur, the corpus luteum degenerates and its secretions stop abruptly. With the stopping of the hormones, the rich blood supply built up in the lining of the uterus sloughs off and leaves the body during menstruation.
The menopause, or change of life, is as natural for women as menstruation and the bearing of children.
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