The internal genital organs form a pathway (the genital tract). This pathway consists of the following:
Vagina (part of the birth canal), where sperm are deposited and from which a baby can emerge
Cervix (the lower part of the uterus), where sperm enter and which opens (dilates) when a pregnant woman is ready to gives birth
Uterus, where an embryo can develop into a fetus
Fallopian tubes (oviducts), where sperm can fertilize an egg after traveling through the cervix and uterus
Ovaries, which produce and release eggs
Sperm can travel up the tract, and eggs down the tract.
Internal Female Reproductive Anatomy
The hymen is a ring of tissue located just inside the opening of the vagina (see figure External Female Genital Organs). The hymen usually encircles the opening. Rarely, it completely covers the opening (called an imperforate hymen), making it impossible for menstrual blood to pass. In such cases, a procedure is done to open the hymen. The hymen may tear at the first attempt at sexual intercourse, or it may be soft and pliable and not tear. The hymen may also be torn during exercise or insertion of a tampon or diaphragm. Tearing usually causes slight bleeding. When the hymen tears, it may be unnoticeable or may form small tags of tissue around the vaginal opening.
Vagina
The vagina is a soft, stretchable tube of muscle tissue about 4 to 5 inches long in an adult woman. It connects the external genital organs to the uterus. The upper part of the vagina is wider and surrounds the cervix (the lower part of the uterus). Some types of birth control (such as a diaphragm or vaginal ring) or drugs are inserted here.
The vagina has a central role in sexual activity and reproduction. It is the passageway for the following:
Sperm to the egg to the uterus and fallopian tubes
Menstrual bleeding or a baby to the outside.
Because the vaginal tissue is soft, its walls can stretch open for examination by a doctor, for sexual intercourse, or for childbirth. After menopause, the vagina becomes less stretchy because estrogen levels decrease. This change can cause pain.
The vagina is lined with a mucous membrane, kept moist by fluids produced by cells on its surface and by secretions from glands in the cervix. A small amount of these fluids may pass to the outside as a clear or milky white vaginal discharge, which is normal. During a woman's reproductive years, the lining of the vagina has folds and wrinkles. Before puberty and after menopause, the lining is smooth.
Uterus and cervix
The uterus is a thick-walled, muscular, pear-shaped organ located in the middle of the pelvis, behind the bladder, and in front of the rectum. The uterus is anchored in position by several ligaments. The main function of the uterus is to sustain a developing fetus.
The uterus consists of the following:
The cervix
The main body (corpus)
The cervix is the lower part of the uterus, which protrudes into the upper part of the vagina. During a pelvic examination, doctors can examine the cervix using a speculum (a metal or plastic instrument that spreads the walls of the vagina apart). Like the vagina, the cervix is lined with a mucous membrane.
Sperm can enter and menstrual blood can exit the uterus through a channel in the cervix (cervical canal). The cervical canal is usually narrow, but during labor, the canal widens to let the baby through.
The cervix is usually a good barrier against bacteria. However, the bacteria that cause sexually transmitted diseases can enter the uterus through the cervix during sexual intercourse.
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The channel through the cervix is lined with cells and glands that secrete mucus. This mucus is thick and impenetrable to sperm until just before ovulation. At ovulation, the mucus becomes clear and elastic (because the level of the hormone estrogen increases). As a result, sperm can swim through the mucus into the uterus to the fallopian tubes, where fertilization can take place.
Almost all pregnancies result from intercourse that occurs during the 3 days before ovulation. However, pregnancies sometimes result from intercourse that occurs up to 6 days before ovulation or during the 3 days after ovulation. For some women, the time between a menstrual period and ovulation varies from month to month. Consequently, pregnancy can occur at different times during a menstrual cycle.
The corpus of the uterus, which consists of muscle tissue, can stretch to accommodate a growing fetus. Its muscular walls contract during labor to push the baby out through the cervix and the vagina. During the reproductive years, the corpus is twice as long as the cervix. After menopause, th uterus and cervix are about the same length.
As part of a woman's reproductive cycle (which usually lasts about a month), the lining of the corpus (endometrium) thickens. If the woman does not become pregnant during that cycle, most of the endometrium is shed and bleeding occurs, resulting in the menstrual period.
Fallopian tubes
The two fallopian tubes, which are about 4 to 5 inches (about 10 to 13 centimeters) long, extend from the upper edges of the uterus toward the ovaries. The tubes do not directly connect with the ovaries. Instead, the end of each tube flares into a funnel shape with fingerlike extensions (fimbriae). When an egg is released from an ovary, the fimbriae guide the egg into the opening of a fallopian tube.
The fallopian tubes are lined with tiny hairlike projections (cilia). The cilia and the muscles in the tube's wall propel an egg downward through the tube to the uterus. The fallopian tube is the usual site of fertilization of the egg by the sperm. After fertilization, the fertilized egg enters the uterus and implants there.
Ovaries
The ovaries are usually pearl-colored, oblong, and about the size of a walnut. They are attached to the uterus by ligaments. In addition to producing female sex hormones (estrogen and progesterone) and some male sex hormones, the ovaries produce and release eggs. The developing egg cells (oocytes) are contained in fluid-filled cavities (follicles) in the wall of the ovaries. Each follicle contains one oocyte.
