The vagina (French: le vagin) is a rather capacious and markedly dilatable musculo-mucous canal, which extends from the uterus to the external genitalia. When collapsed it is markedly flattened from before backward, so that its lumen corresponds to the letter H, the anterior and posterior walls being in contact, while small recesses occur on either side. The anterior wall is usually concave posteriorly, the posterior wall being correspondingly convex anteriorly.

The anterior wall is shorter than the posterior, and is about 6 to 7 cm in length, the posterior wall being about 15 cm longer. This is due to the fact that the axis of the cervix holds an oblique relation with the axis of the vagina, the vaginal portion of the cervix projecting into the vagina in such a manner that the lips of the external os are of unequal length. The anterior wall is inserted into the base of the short anterior lip and the posterior wall into the longer posterior lip, so that the vaginal wall is firmly attached to the uterine wall and the vaginal mucous membrane is immediately reflected upon the lips of the external os. In this manner there is formed a narrow circular space between the external os and the vaginal wall, the fornix of the vagina, that portion of it lying in front of the external os uteri being termed the anterior fornix, that behind the external os the posterior fornix, and the intervening space the lateral fornix. On account of the great length of the posterior lip of the external os the posterior vaginal fornix is the deepest. The vagina is extremely dilatable, so that both its length and its breadth are subject to great variation; in virgins and nulliparae it is of smaller caliber than in multipara, and its entrance or introitus is always the narrowest portion.

The anterior vaginal wall is in contact with the fundus of the bladder and with the urethra, and is rather firmly adherent to both of these structures. It is also intimately related with the ureter, which is situated between the upper portion of the anterior vaginal wall and the bladder.

About 1 to 1.5 cm. of the upper portion of the posterior vaginal wall (the posterior fornix and the contiguous portion of the lateral one) are invested by the peritoneum of the recto-uterine pouch, but the remaining portions have no peritoneal covering whatever. The lower portion of the posterior vaginal wall is in contact with the rectum, but the upper portion is separated from this structure by the recto-uterine pouch.* The lateral walls of the vagina are surrounded by a venous plexus and, like the entire vaginal circumference, are in contact with the muscles and fascia of the pelvic floor, especially with the urogenital trigone and the levatores ani. The lower portion of the vagina is surrounded by the sphincter-like fibers of the mm. bulbocavernosi.

With the exception of the posterior vaginal fornix, which possesses a serous coat, the vaginal wall consists of a fibrous, a muscular, and a mucous coat. The fibrous coat is adherent to the neighboring viscera (the bladder, the urethra, and the rectum), and the muscular coat is well developed, though weaker than that of the uterus, with which it is directly continuous at the attachment of the vagina to the cervix. The mucous membrane contains no glands, and a submucous layer is wanting, as in the uterus. Upon both the anterior and the posterior vaginal walls the mucous membrane forms curved transverse folds, the vaginal ruga, which together with a longitudinal elevation on each wall form the columnce rugarum (anterior and posterior). The lower portion of the columna rugarum anterior is especially prominent and is produced by the lower portion of the urethra, which projects into the vagina as the urethral carina and is even visible in the vaginal vestibule. The folds of the vaginal mucous membrane are rather firm and sharply defined in virgins, but they gradually disappear after repeated births; the mucous membrane covering the vaginal portion of the cervix possesses no folds whatever.

At the vaginal entrance of virgins a fold proceeds from the posterior vaginal wall which is known as the hymen (hymen jeminus). When tense, it is usually sickle-shaped, since it generally disappears upon the lateral wall of the vaginal entrance, but it is not infrequently continued around the anterior circumference of the vaginal entrance, so that it is circular with an eccentric opening. The margin of the sickle-shaped hymen is usually smooth, while that of the circular one is frequently notched (hymen fimbriates), and the opening in the fimbriate hymen is rarely central. When the thighs are adducted the opening of the (sickle-shaped) hymen appears like a median fissure, the lateral portions of the hymen being thrown into folds. The hymen is usually torn during the first coition, but its remains persist for a long time, and, particularly after the birth of a child, they form short irregular lobes or warts, the caruncuke hymenales.

The upper portion of the vagina is nourished by the uterine artery, which runs in the immediate proximity of this portion of the lateral vaginal wall on its way to reach the uterine cervix. The middle portion receives the inferior vesical artery, and the lower portion is supplied by the middle hemorrhoidal and the internal pudic arteries.

The veins, like those of almost all the pelvic viscera, form a plexus upon the vaginal wall and empty into the internal iliac vein.

The lymphatics of the lower portion of the vagina and of the region of the hymen pass with those of the labia minora to the inguinal glands and partly also to lymphatic glands situated within the pelvis. The lymphatics of the middle portion pass independently to the hypogastric and iliac glands, while those of the upper portion empty into the same glands along with the lymphatics of the cervix.

The nerves for the lower portion of the vagina are derived from the pudic, those for the upper portion from the nerves for the uterus.

From Human Anatomy (1909) by DR. Johannes Sobotta (1869-1945) Professor of Anatomy in the university of Wurzburg