The vaginal wall (Fig. 23.27) consists of the following.  An inner mucosal layer has numerous transverse folds or rugae (see Fig. 23.1) and is lined with stratified squamous epithelium (Fig. 23.28). Connective tissue papillae from the underlying lamina propria project into the epithelial layer. In humans and other primates, keratohyalin granules may be present in the epithelial cells, but under normal conditions, keratinization does not occur. Therefore, nuclei can be seen in epithelial cells throughout the thickness of the epithelium.
 An intermediate muscular layer is organized into two sometimes indistinct, intermingling smooth muscle layers, an outer longitudinal layer, and an inner circular layer. The outer layer is continuous with the corresponding layer in the uterus and is much thicker than the inner layer. Stria ted muscle fibers of the bulbospongiosus muscle are present at the vaginal opening (Plate 101, page 890).
 An outer adventitial layer is organized into an inner dense connective tissue layer adjacent to the muscularis and an outer loose connective tissue layer that blends with the adventitia of the surrounding structures. The inner layer contains numerous elastic fibers that contribute to the elasticity and strength of the vaginal wall. The outer layer contains numerous blood and lymphatic vessels and nerves.
The vagina possesses a stratified, squamous nonkeratinized epithelium and lacks glands.
The lumen of the vagina is lined by stratifed squamous, nonkeratinized epithelium. Its surface is lubricated mainly by mucus produced by the cervical glands. The greater and lesser vestibular glands located in the wall of the vaginal vestibule produce additional mucus that lubricates the vagina. Glands are not present in the wall of the vagina. The epithelium of the vagina undergoes cyclic changes during the menstrual cycle. Under the influence of estrogens, during the follicular
FIGURE 23.27 • Photomicrograph of a human vagina. This low-magnification H&E–stained specimen of the vaginal wall shows two of three layers of the vagina: the mucosal layer and the muscular layer (the outer layer, the adventitia, is not included). The mucosal layer consists of a stratified squamous epithelium and the underlying connective tissue. The epithelial connective tissue boundary is typically very irregular, with prominent papillae projecting into the undersurface of the epithelium. The muscular layer is seen only in part; it consists of irregularly arranged bundles of smooth muscle cells. Also, the deep region of the connective tissue contains a rich supply of blood vessels that supply the various layers of the vaginal wall. 40.
phase, the epithelial cells synthesize and accumulate glycogen as they migrate toward the surface. Cells are continuously desquamated, but near or during the menstrual phase, the superficial layer of the vaginal epithelium may be shed.
The lamina propria exhibits two distinct regions. The outer region immediately below the epithelium is a highly cellular loose connective tissue. The deeper region, adjacent to the muscular layer, is denser and may be considered a submucosa. The deeper region contains many thin-walled veins that simulate erectile tissue during sexual arousal. Numerous elastic fibers are present immediately below the epithelium, and some of the fibers extend into the muscular layer. Many lymphocytes and leukocytes (particularly neutrophils) are found in the lamina propria and migrate into the epithelium. Solitary lymphatic nodules may also be present. The number of lymphocytes and leukocytes in the mucosa and vaginal lumen dramatically increases around the time of menstrual flow. The vagina has few general sensory nerve endings. The sensory nerve endings that
FIGURE 23.28 • Photomicrograph of the vaginal mucosa.