V. iliaca interna, internal iliac vein, in the form of a short but thick trunk located behind the artery of the same name. The tributaries, from which the internal iliac vein is composed, correspond to the arterial branches of the same name, usually outside the pelvis, these tributaries are in double number, and they are single in the pelvic cavity. In the area of the tributaries of the internal iliac vein, a number of venous plexuses are formed, which anastomose among themselves.
1. Plexus venosus sacralis is composed of the sacral veins – lateral and median.
2. Plexus venosus rectalis – plexus in the walls of the rectum. There are three plexuses: submucosal, subfascial and subcutaneous. The submucosal, or internal, venous plexus, plexus rectalis internus, in the area of the lower ends of the columnae anales represents a series of venous nodules arranged in a ring. The diverting veins of this plexus perforate the muscular layer of the intestine and merge with the veins of the subfascial, or external, plexus, plexus rectalis externus. From the last go v. rectalis superior and vv. rectales mediae, accompanying co-arteries. The first through the inferior mesenteric vein is poured into the portal vein system, the second – into the system of the inferior vena cava through the internal iliac vein. In the area of the external sphincter of the anus, a third plexus is formed — subcutaneous, plexus subcutaneus ani, from which the vv. rectales inferiores flowing into v. pudenda interna.
3. Plexus venosus vesicalis is located in the area of the bottom of the bladder; through vv. vesicales blood is poured from this plexus into the internal iliac vein.
4. Plexus venosus prostaticus is located between the bladder and the pubic symphysis, encompassing the male prostate gland and seminal vesicles. Unpaired v. Merges into plexus venosus prostaticus. dorsalis penis. In a woman, this vein corresponds to v. dorsalis clitoridis.
5. Plexus venosus uterinus and plexus venosus vaginalis women are located in the wide ligaments on the sides of the uterus and further down the side walls of the vagina; blood from them through the ovarian vein (plexus pampiniformis), mainly through v. uterina, enters the internal iliac vein.