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(a) Light micrograph of a uterine tube (250x micrograph enlarged to 800x). (b) Scanning electron micrograph of ciliated cells that line the uterine tube (4,000x).

The upper two-thirds, or body, of the uterus has a dome-shaped top, called the fundus, and is joined by the uterine tubes, which enter its wall at its broadest part. The lower one-third, or neck, of the uterus is called the cervix. This tubular part extends downward into the upper portion of the vagina. The cervix surrounds the opening called the cervical orifice (ostium uteri), through which the uterus opens to the vagina.

The uterine wall is thick and composed of three layers (fig. 22.29). The endometrium is the inner mucosal layer lining the uterine cavity. It is covered with columnar epithelium and contains abundant tubular glands. The myometrium, a very thick, muscular layer, largely consists of bundles of smooth muscle fibers in longitudinal, circular, and spiral patterns and is interlaced with connective tissues. During the monthly female reproductive cycles and during pregnancy, the endometrium and myometrium extensively change. The perimetrium consists of an outer serosal layer, which covers the body of the uterus and part of the cervix.

Vagina

The vagina is a fibromuscular tube, about 9 centimeters long, that extends from the uterus to the outside. It conveys uterine secretions, receives the erect penis during sexual intercourse, and provides the open channel for the offspring during birth.

The vagina extends upward and back into the pelvic cavity. It is posterior to the urinary bladder and urethra, anterior to the rectum, and attached to these structures by connective tissues. The upper one-fourth of the vagina is separated from the rectum by a pouch (rectouterine pouch). The tubular vagina also surrounds the end of the cervix, and the recesses between the vagi-

Lumen

Endometrium

Myometrium

Perimetrium

Lumen

Endometrium

Myometrium

Perimetrium

Figure 22.29

Light micrograph of the uterine wall (10.5x).

Figure 22.29

Light micrograph of the uterine wall (10.5x).

nal wall and the cervix are termed fornices (sing., fornix). The fornices are clinically important because they are thin-walled and allow the physician to palpate the internal abdominal organs during a physical examination. Also, the posterior fornix, which is somewhat longer than the others, provides a surgical access to the peritoneal cavity through the vagina.

The vaginal orifice is partially closed by a thin membrane of connective tissue and stratified squamous epithelium called the hymen. A central opening of varying size allows uterine and vaginal secretions to pass to the outside.

The vaginal wall consists of three layers. The inner mucosal layer is stratified squamous epithelium and is drawn into many longitudinal and transverse ridges (vaginal rugae). This layer lacks mucous glands; the mucus found in the lumen of the vagina comes from the glands of the cervix and the vestibular glands at the mouth of the vagina.

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