Figure 19-8 Female reproductive system. The enlargement (right) shows ovulation.
The accessory organs in the female are the oviducts, the uterus, the vagina, the greater vestibular glands, and the vulva and perineum.
The Oviducts: The tubes that transport the ova in the female reproductive system, the oviducts, are also known as uterine tubes, or fallopian tubes. Each is a small, muscular structure, nearly 12.5 cm (5 inches) long, extending from a point near the ovary to the uterus (womb). There is no direct connection between the ovary and this tube. The ovum is swept into the oviduct by a current in the peritoneal fluid produced by the small, fringelike extensions called fimbriae that are located at the edge of the tube’s opening into the abdomen (see Fig. 19-8) Unlike the sperm cell, the ovum cannot move by itself. Its progress through the oviduct toward the uterus depends on the sweeping action of cilia in the tube’s lining and on peristalsis of the tube. It takes about 5 days for an ovum to reach the uterus from the ovary.
Figure 19-10 The uterus as seen under the microscope. The photomicrographs show the myometrium and endometrium and illustrate the changes that occur in the endometrium during the menstrual cycle. (A) Proliferative phase (first part of cycle). (B) Secretory phase (second part of cycle).
The Uterus: The oviducts lead to the uterus, an organ in which a fetus can develop to maturity. The uterus is a pear-shaped, muscular organ about 7.5 cm (3 inches) long, 5 cm (2 inches) wide, and 2.5 cm (1 inch) deep. (The organ is typically larger in women who have borne children and smaller in postmenopausal women). The superior portion rests on the upper surface of the urinary bladder; the inferior portion is embedded in the pelvic floor between the bladder and the rectum. The wider upper region of the uterus is called the corpus, or body; the lower, narrower region is the cervix, or neck. The small, rounded region above the level of the tubal entrances is known as the fundus (see Fig. 19-8). The broad ligaments support the uterus, extending from each side of the organ to the lateral body wall. Along with the uterus, these two portions of peritoneum form a partition dividing the female pelvis into anterior and posterior areas. The ovaries are suspended from the broad ligaments, and the oviducts lie within the upper borders. Blood vessels that supply these organs are found between the layers of the broad ligament (see Fig. 19-8). The muscular wall of the uterus is called the myometrium (Fig. 19-10). The lining of the uterus is a specialized epithelium known as endometrium. This inner layer changes during the menstrual cycle, first preparing to nourish a fertilized egg, then breaking down if no fertilization occurs to be released as the menstrual flow. The cavity inside the uterus is shaped somewhat like a capital T, but it is capable of changing shape and dilating as a fetus develops.
The Vagina: The cervix leads to the vagina, the distal part of the birth canal, which opens to the outside of the body. The vagina is a muscular tube about 7.5 cm (3 inches) long connecting the uterine cavity with the outside. The cervix dips into the superior portion of the vagina forming a circular recess known as the fornix. The deepest area of the fornix, located behind the cervix, is the posterior fornix (Fig. 19-11). This recess in the posterior vagina lies adjacent to the most inferior portion of the peritoneal cavity, a narrow passage between the uterus and the rectum named the cul-de-sac (from the French meaning “bottom of the sack”). This area is also known as the rectouterine pouch or the pouch of Douglas. A rather thin layer of tissue separates the posterior fornix from this region, so that abscesses or tumors in the peritoneal cavity can sometimes be detected by vaginal examination. The lining of the vagina is a wrinkled mucous membrane similar to that found in the stomach. The folds (rugae) permit enlargement so that childbirth usually does not tear the lining. In addition to being a part of the birth canal, the vagina is the organ that receives the penis during sexual intercourse. A fold of membrane called the hymen may sometimes be found at or near the vaginal canal opening (see Fig. 19-12).
The Greater Vestibular Glands: Just superior and lateral to the vaginal opening are the two mucus-producing greater vestibular glands (see Fig. 19-8). These glands secrete into an area near the vaginal opening known as the vestibule. Like the Cowper glands in males, these glands provide lubrication during intercourse. If a gland becomes infected, a surgical incision may be needed to reduce swelling and promote drainage.
The Vulva and the Perineum: The external parts of the female reproductive system form the vulva, which includes two pairs of lips, or labia; the clitoris, which is a small organ of great sensitivity; and related structures. Although the entire pelvic floor in both the male and female is properly called the perineum, those who care for pregnant women usually refer to the limited area between the vaginal opening and the anus as the perineum or obstetrical perineum.
Figure 19-11 Female reproductive system (sagittal section). This view shows the relationship of the reproductive organs to each other and to other structures in the pelvic cavity.
Figure 19-12 External parts of the female reproductive system. Related structures are also shown.