The vagina is the fibromuscular tube of the female reproductive tract that leads to the exterior of the body. The wall of the vagina consists of three layers: a mucosa, a muscularis, and an adventitia. The epithelium of the mucosa is nonkeratinized stratified squamous. It undergoes changes that correspond to the ovarian cycle. The amount of glycogen stored in the epithelial cells increases under the influence of estrogen, whereas the rate of desquamation increases under the influence of progesterone. The glycogen liberated from the desquamated cells is fermented by lactobacilli vaginalis, producing lactic acid that acidifies the vaginal surface and inhibits colonization by yeasts and potentially harmful bacteria. The vagina has certain histologic similarities to the proximal portion of the alimentary canal but is distinguished by the following features: The epithelium does not keratinize, and except for the deepest layers, the cells appear to be empty in routine H&E sections; the mucosa contains neither glands nor a muscularis mucosae; the muscle is smooth and not well ordered. This should be contrasted with the oral cavity, pharynx, and upper part of the esophagus in which the muscle is striated. The more distal portion of the esophagus, which contains smooth muscle, can be distinguished easily from the vagina because it has a muscularis mucosae.
Vagina, human, H&E ×90.
The mucosa of the vagina consists of a stratified squamous epithelium (Ep) and an underlying fibrous connective tissue (CT) that often appears more cellular than other fibrous connective tissue. The boundary between the two is readily identified because of the conspicuous staining of the closely packed small cells of the basal layer (B) of the epithelium. Connective tissue papillae project into the underside of the epithelium, giving the epithelial– connective tissue junction an uneven appearance. The papillae may be cut obliquely or in cross section and thus may appear as connective tissue islands (arrows) within the lower portion of the epithelium. The epithelium is characteristically thick and although keratohyaline granules may be found in the
Mucosa, vagina, human H&E ×110.
This is a higher magnification of the epithelium that includes the area outlined by the rectangle in upper figure (turned 90 ). The obliquely cut and cross-sectioned portions of connective tissue papillae that appear as connective tissue islands in the
Mucosa, vagina, human H&E ×225.
This is a higher-magnification micrograph of the basal portion of the epithelium (Ep) between connective tissue papillae. Note the regularity and dense packing of the basal epithelial cells. They are the stem cells for the stratified squamous epithelium. Daughter cells of these cells migrate toward the surface
Muscularis, vagina, human, H&E ×125.
This higher-magnification micrograph of the smooth muscle of the vaginal wall emphasizes the irregularity of the arrangement of the muscle bundles. At the right edge of the figure is a bundle of smooth muscle cut in a longitudinal section (SML).