THE VAGINA.
The vagina is a musculo-membranous canal passing from the vulva to the uterus.
It is situated in the pelvic cavity above the rectum and below the bladder and the urethra.
• Its direction is oblique from above downward, and from behind for ward. According as the bladder is full or empty, it forms, with the uterus, an obtuse angle with an anterior concavity, or a right angle.
The two walls are of unequal length. The anterior wall is from 3.1 to 3.2 inches long, the posterior from 3.2 to 3.9 inches. (Sappey.) According to Pajot the axial length of the vagina is 4.6 inches, according to Cazeaux from 4.2 to 5 inches. This length is not absolutely fixed, and in regresses in particular the vagina is usually longer than in Europeans. In some women, on the contrary, the vagina is short, being only from 1.5 to 1.9 inches long. Its calibre varies in different parts. Its narrowest point is where it joins the vulva; just behind this point the vagina begins to dilate, and continues to increase from below upward. Nevertheless, we may say that the average transverse and antero-posterior dimensions are from 1.1 to 1.5 inches in women who have had no children, and from 2.3 to 2.6 inches in others. The walls are besides very extensible, even reaching the sides of the pelvis when the head of the child passes. Pajot rightly observed that this extensibility is and that it does not permit nearly so great an increase in the longitudinal direction.
The vagina presents for consideration, an internal surface, a superior and an inferior extremity, and an external surface.
External Surface.—This has an anterior, a posterior and two lateral walls.
Anterior Wall.—It is shorter than the posterior wall, and above it lies the inferior wall of the bladder, and of the urethra. A thin cellular tissue unites it to the lower end of the bladder; it also lies under the terminal portion of the ureters. For the remainder of its course the anterior wall lies below the canal of the urethra, which is united to it by muscular fibres. it even seems to form a groove to hold the canal.
• Posterior Wall.—Behind, it is covered by the peritoneum for a dis tance not exceeding .46 to .58 inches. Below the recto-vaginal cul-de-sac • the rectum adheres to it by cellular tissue. This junction of the rectum and vagina forms the recto-vaginal fold. Slender above, this partition gradually becomes thicker on account of the increase of the cellulo-fatty layer, and the distance apart of the two organs. The vagina is separated from the rectum below by a space of 1.1 to 1.5 inches. This space forms a triangle, the apex of which is the point of juncture of the rectum and vagina, and the sides of which are formed by the opposite walls of the rectum and vagina.
The edges or lateral walls correspond, from above downward, to the most inclined part of the broad ligament, to the adipose tissue of the floor of the cavity, to the superior pelvic aponeurosis, and to the levator ani. Below, these edges are covered by the bulbs of the vagina.
The internal surface is broken, along the median line, by two projec tions which form the columns of the vagina. They extend throughout its whole length. There are also transverse folds which are more marked in the anterior part of the vagina.
The superior or uterine extremity is attached to the neck of the uterus. The posterior wall being inserted higher than the anterior, the mucous membrane of the vagina, in folding about the neck, forms a cul-de-sac which may be divided into two, a posterior and an anterior cul-de-sac.
The anterior opening of the vagina is continuous with the posterior circumference of the vulva. It forms an oval orifice. When partially open it presents, on its superior part, a rough and round tubercle, the anterior tubercle of the vagina, and above this tubercle the orifice of the urethra.
Below, the vagina forms a depression, which separates it from the perineum, and which is called the fosse, navicularis.