Page:Anatomy of the Human Body (1918).djvu/682

682 it then passes behind the body of the pancreas and opens into the lienal vein; sometimes it ends in the angle of union of the lienal and superior mesenteric veins.

Tributaries.—The inferior mesenteric vein receives the sigmoid veins from the sigmoid colon and iliac colon, and the left colic vein from the descending colon and left colic flexure.

The Superior Mesenteric Vein(v. mesenierica superior) returns the blood from the small intestine, from the cecum, and from the ascending and transverse portions of the colon. It begins in the right iliac fossa by the union of the veins which drain the terminal part of the ileum, the cecum, and vermiform process, and ascends between the two layers of the mesentery on the right side of the superior mesenteric artery. In its upward course it passes in front of the right ureter, the inferior vena cava, the inferior part of the duodenum, and the lower portion of the head of the pancreas. Behind the neck of the pancreas it unites with the lienal vein to form the portal vein.

Tributaries.—Besides the tributaries which correspond with the branches of the superior mesenteric artery, viz., the intestinal, ileocolic, right colic, and middle colic veins, the superior mesenteric vein is joined by the right gastroepiploic and pancreaticoduodenal veins.

The right gastroepiploic vein (v. gastroepiploica dextra) receives branches from the greater omentum and from the lower parts of the antero-superior and posteroinferior surfaces of the stomach; it runs from left to right along the greater curvature of the stomach between the two layers of the greater omentum.

The pancreaticoduodenal veins (vv. pancreaticoduodenales) accompany their corresponding arteries; the lower of the two frequently joins the right gastroepiploic vein.

The Coronary Vein (v. coronaria ventriculi; gastric vein) derives tributaries from both surfaces of the stomach; it runs from right to left along the lesser curvature of the stomach, between the two layers of the lesser omentum, to the esophageal opening of the stomach, where it receives some esophageal veins. It then turns backward and passes from left to right behind the omental bursa and ends in the portal vein.

The Pyloric Vein is of small size, and runs from left to right along the pyloric portion of the lesser curvature of the stomach, between the two layers of the lesser omentum, to end in the portal vein.

The Cystic Vein (v. cystica) drains the blood from the gall-bladder, and, accompanying the cystic duct, usually ends in the right branch of the portal vein.

Parumbilical Veins (vv. parumbilicales).—In the course of the ligamentum teres of the liver and of the middle umbilical ligament, small veins (parumbilical) are found which establish an anastomosis between the veins of the anterior abdominal wall and the portal, hypogastric, and iliac veins. The best marked of these small veins is one which commences at the umbilicus and runs backward and upward in, or on the surface of, the ligamentum teres between the layers of the falciform ligament to end in the left portal vein.

Collateral venous circulation to relieve portal obstruction in the liver may be effected bycommunications between (a) the gastric veins and the esophageal veins which often project as a varicose bunch into the stomach, emptying themselves into the hemiazygos vein; (b) the veins of the colon and duodenum and the left renal vein; (c) the accessory portal system of Sappey, branches of which pass in the round and falciform hgaments (particularly the latter) to unite with the epigastric and internal mammary veins, and through the diaphragmatic veins with the azygos; a single large vein, shown to be a parumbilical vein, may pass from the hilus of the liver by the round hgament to the umbihcus, producing there a bunch of prominent varicose veins known as the caput medusæ; (d) the veins of Retzius, which connect the intestinal veins with the inferior vena cava and its retroperitoneal branches; (e) the inferior mesenteric veins, and the hemorrhoidal veins that open into the hypogastrics; (f) very rarely the ductus venosus remains patent, affording a direct connection between the portal vein and the inferior vena cava.