The vagina is a fibromuscular tube that joins internal reproductive organs to the external environment

The vagina is a fibromuscular sheath extending from the cervix to the vestibule, which is the area between the labia minora. In a virgin, the opening into the vagina may be surrounded by the hymen, folds of mucous membrane extending into the vaginal lumen. The hymen or its remnants are derived from the endodermal membrane that separated the developing vagina from the cavity of the definitive urogenital sinus in the embryo.

The vaginal wall (Fig. 22.27) consists of an

• Inner mucosal layer, which has numerous transverse folds or rugae (see Fig. 22.1) and is lined with stratified squamous epithelium (Fig. 22.28). Connective tissue papillae from the underlying lamina propria project into the epithelial layer. In humans and other primates, kera-tohyalin 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.

• Intermediate muscular layer, which 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. Striated muscle fibers of the bulbospongiosus muscle are present at the vaginal opening.

stratified squamous epithelium a m-

mucosal layer blood vessels

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