The vaginal opening is below the vestibule and above the perineum. It is partially closed by the hymen, a fold of mucous membrane disposed irregularly around the outlet, somewhat after the fashion of a circular curtain. The hymen is ragged or more or less scalloped in outline, and varies greatly in size in different women, in some instances extending so far over the opening as nearly or quite to close it.
The fossa navicularis is a depressed space between the hymen and fourchette, so named because of its boat-like shape.
The Bartholin glands, probably the largest and most important of the vulvo-vaginal glands, are situated one on each side of the vagina and open into the groove between the hymen and labia minora. Reference is made to these glands because of the danger of their becoming infected. A gonorrheal infection of these glands is particularly troublesome.
The perineum is a pyramidal structure of connective tissue and muscle which occupies the space between the rectum and vagina, and by forming the floor of the pelvis serves as a support for the pelvic organs. The lower and outer surface of this mass, representing the base of the pyramid, lies between the vaginal opening and the anus and is covered with skin. As the anterior part of the perineum is incorporated in the posterior wall of the vagina, the entire structure becomes stretched and flattened when the vagina is dilated during labor by the passage of the child’s head.
Unless very carefully guarded at the time of delivery, and often even then, the perineum gives way under the great tension undergone at that time, and a tear is the result. The injury may be only a slight nick in the mucous membrane or it may extend to, or into the levator ani, the most important muscle of the perineal body, or if a “complete tear” will extend all the way through the perineum and completely through the sphincter ani. Such a tear is lamentable, as a break in the ring-shaped sphincter muscle guarding the anal opening robs a woman of control of her bowels, and is repaired with difficulty.
BREASTS
The breasts are large, specially modified skin glands of the compound, racemose or clustering type, embedded in fat and connective tissue and abundantly supplied with nerves and blood vessels. They are situated quite remotely from the pelvic organs, but because of the intimate functional relation between the two, the breasts of the female may be regarded as accessory glands of the generative system. They exist in the male, also, but only in a rudimentary state.
Although the breasts sometimes contain milk during infancy, their true function is to secrete, in the parturient woman, suitable nourishment for the human infant during the first few months of its life.
These glands are symmetrically placed, one on each side of the chest, and occupy the space between the second and sixth ribs extending from the margin of the sternum almost to the mid-axillary line. A bed of connective tissue separates them from the underlying muscles and the ribs. (Fig. [14].)
They vary in size and shape at different ages, and with different individuals, particularly in women who have borne and nursed children, when they tend to become pendulous. But in general they are hemispherical or conical in shape with the nipple protruding from one-quarter to one-half inch from the apex. The nipples are largely composed of sensitive, erectile tissue and become more rigid and prominent during pregnancy and at the menstrual periods. Their surfaces are pierced by the orifices of the milk ducts, which are fifteen or twenty in number. (Fig. [15].)