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The internal female sex organs are the ovaries, the fallopian tubes (oviducts), the womb (uterus) and the vagina.
The ovaries
The ovaries are almond-shaped paired organs. They have two important functions
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to supply fertilizable eggs and
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to produce the female sex hormones estrogen and progesterone.
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The ovaries contain structures called
follicles which consist of the egg itself and an outer covering of cells. During each menstrual cycle follicles mature and produce follicular hormones (estrogens). At ovulation a mature egg (ovum) is released from the ovary. The remaining cells of the ruptured follicle develop into the corpus luteum ("yellow body") which produces the hormone progesterone.
The fallopian tubes
The fallopian tubes, like the ovaries, are paired organs. They are each about 15 cm (5 inches) long and about the thickness of a pencil. They widen towards the ovaries forming a funnel-shaped opening with finger-like projections called fimbriae. The function of the fallopian tubes is to pick up the mature ovum after ovulation. In order to do this, the fimbriae place themselves over the ovary and the ovum is drawn into the tube by rhythmic contractions.
The fallopian tube is lined with tiny hairs (cilia) and glands. Muscular contractions, the movement of the cilia and the fluid secreted by the glands help transport the ovum to the uterus. The fallopian tubes are also the site where fertilization takes place.
The uterus (womb)
The uterus is a pear-shaped hollow organ about 7 cm (3 inches) long. If conception occurs the fertilized egg becomes embedded in the uterus which holds the developing fetus until birth.
The uterus has a strong muscular wall which expands during pregnancy to accommodate the growing fetus. During birth the muscular wall contracts rhythmically. These contractions are what are known as labor pains.
The uterus is lined with a mucous membrane called the endometrium. In sexually mature women the lining undergoes certain changes in the course of the menstrual cycle. After every menstrual period it becomes thicker and more richly supplied with blood in preparation for implantation of a fertilized ovum. If conception does not take place the endometrium is shed as part of the menstrual flow.
The neck of the uterus or cervix is the narrow portion at the lower end of the uterus. The end which opens into the vagina is called the cervical os. The cervix is sealed with a plug of thick mucus. This plug of cervical mucus prevents sperm from entering the uterus and also protects against the entry of germs. For a few days around the time of ovulation, however, the cervical mucus becomes thinner and the cervical os widens so that sperm can enter and travel upwards to meet the mature ovum. Some
natural family planning methods make use of these typical monthly changes in the cervical fluid to determine the fertile days of the cycle.
The vagina
The vagina is an elastic muscular tube which takes up the penis during sexual intercourse. During childbirth it forms part of the birth canal.
The vaginal wall is lined with a mucous membrane and coated with acid secretions which protect against ascending germs.
The mucous membrane lining the vagina is composed of several layers of cells. During the menstrual cycle the structure and thickness of these cell layers change under the influence of the sex hormones estrogen and progesterone. Examination of a scraping of cells (smear) under the microscope gives the doctor information about a woman's hormone levels.
Sex hormones regulate the functioning of the sex organs
The female sex hormones estrogen and progesterone regulate the functions of the female sex organs. They also play an important role in keeping the body healthy.
Production of the hormones in the ovaries is controlled by the hypothalamus (part of the forebrain) and the pituitary gland.
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