The vagina is a muscular, extensible elastic tube about 10 cm long (3.9 in), which extends from the cervix to the external genitalia. The cervix protrudes into the vagina. The part of the vagina surrounding the cervix is the fornix. In women who have not had inter-course, a thin epithelial fold—the hymen—partially or fully covers the opening of the vagina. Skeletal muscles similar to that present in the male, the bul-bospongiosus, extend along the sides of the vaginaand help constrict the opening. The vagina is lined by stratified squamous epithelium and houses many harmless bacteria, whose acidic secretions prevent harmful organisms from thriving there.
The perineum denotes the region between the thighs and buttocks that houses the external genitalia and anus in both sexes. The perineum extends to the pu-bic symphysis anteriorly, to the ischial tuberosities laterally, and to the coccyx posteriorly.