Along this variously constructed canal, at different periods in the life of the individual, pass the matured ovum, the menstrual flow, the uterine secretions, the fetus, the placenta and lochia, (the discharge which occurs during the puerperium).
Although the bladder and rectum are not organs of reproduction, they are contained in the pelvic cavity and lie in such close proximity to the internal genitalia that at least a passing word must be devoted to their description.
The bladder is a sac of connective tissue which serves as a reservoir for the urine and is situated behind the symphysis pubis and in front of the uterus and vagina. Urine is conducted into the bladder by the ureters, two slender tubes running down on each side from the basin of the kidney across the pelvic brim to the upper part of the bladder, which they enter somewhat obliquely, at about the level of the cervix. It is thought that pressure of the enlarged pregnant uterus upon the ureters at this point may be one factor in the causation of pyelitis, a frequent complication of pregnancy. The bladder empties itself through the urethra, a short tube which terminates in the meatus urinarius, a tiny opening in the vulva.
The rectum, the lowest segment of the intestinal tract, is situated in the pelvic cavity behind and to the left of the uterus and vagina. It extends downward from the sigmoid flexure of the colon to its termination in the anal opening. The anus is a deeply pigmented, puckered opening situated an inch and a half or two inches behind the vagina. It is guarded by two bands of strong circular muscles, the internal and external sphincter ani. The skin covering the surface of the body extends upward into the anus where it becomes highly vascular and merges into the mucous lining of the rectum. Pressure exerted during pregnancy by the enlarged uterus is felt in both the rectum and bladder, frequently causing a good deal of discomfort and almost painful desire to evacuate their contents.
The blood vessels in the anal lining just within the external sphincter sometimes become engorged and inflamed, even bleeding during pregnancy, as a result of the pressure exerted by the greatly enlarged uterus. The distended blood vessels, which in this condition are called hemorrhoids, not infrequently protrude from the anus and become very painful.
After having considered the structure and relative positions of the pelvic organs one is able to picture more clearly the arrangement and disposition of the uterine ligaments, all of which are formed by folds of the peritoneum. They are twelve in number, five pairs and two single ligaments, namely: two broad, two round, two utero-sacral, two utero-vesical, two ovarian, one anterior and one posterior ligament.
The broad ligaments are in reality one continuous structure formed by a fold of the peritoneum, which drops down over the uterus, investing the fundus, body, part of the cervix, and part of the posterior wall of the vagina. It unites on each side of the uterus to form a broad, flat membrane which extends laterally to the pelvic wall, dividing the pelvic basin into an anterior and posterior compartment, containing respectively the bladder and rectum. Between the folds of the broad ligament are situated the ovaries and ovarian ligaments, the Fallopian tubes, the round ligaments and a certain amount of muscle and connective tissue, blood vessels, lymphatics and nerves.
The round ligaments, one on each side, are narrow, flat bands of connective tissue derived from the peritoneum and muscle prolonged from the uterus, and containing blood and lymph vessels and nerves. They pass upward and forward from their uterine origin just below and in front of the tubal entrance, finally merging in the mons veneris and labia majora.
The utero-sacral ligaments, of which there is one on each side, arise in the uterus and, extending backward, serve to connect the cervix and vagina with the sacrum.
The utero-vesical ligaments, one on each side, extend forward and connect the uterus and bladder.