Hymen

The hymen is a thin fold of mucous membrane situated at the orifice of the vagina; the inner edges of the fold are normally in contact with each other, and the vaginal orifice appears as a cleft between them.

The hymen varies much in shape. When stretched, its commonest form is that of a ring, generally broadest posteriorly; sometimes it is represented by a semilunar fold, with its concave margin turned toward the pubes. Occasionally it is cribriform, or its free margin forms a membranous fringe. It may be entirely absent, or may form a complete septum across the lower end of the vagina; the latter condition is known as an imperforate hymen. 

It may persist after copulation, so that its presence cannot be considered a sign of virginity. When the hymen has been ruptured, small rounded elevations known as the carunculæ hymenales are found as its remains.

Between the hymen and the frenulum of the labia is a shallow depression, named the navicular fossa.