922 



HUMAN ANATOMY. 



3. The Inferior Mesenteric Vein. — The inferior mesenteric vein (v. mesen- 

 terica inferior) (^Fig. 774) is formed by the junction of the superior hemorrhoidal and 

 sigmoid veins opposite the sigmoid flexure of the colon, and passes upward in 

 company with the corresponding artery. It is continued on, however, beyond the 

 point where the artery arises from the abdominal aorta, lying behind the peritoneum 

 slightly medial to the ascending colon, and, finally, it passes beneath the pancreas 



Fig. 



Ascending colon 



Middle colic vein. 



Right colic vein, 



Superior 



mesenteric vein 



lleo-colic vein 



Caecum 



Transverse colon 



Descending colon 



I-eft colic vein 



Pancreas 



Inferior mesenteric vein 

 Superior mesenteric artery 

 Duodenum, transverse part 

 Jejunum 



Veins of the small intestine 



Coils of ileum 



Superior mesenteric vein and its tributaries ; transverse colon 

 has been pulled upward. 



to open usually into the splenic vein not far from its union with the superior 

 mesenteric. Occasionally it opens into the latter \'ein (Fig. 774) or else equally 

 into both, thus taking a direct part in the formation of the portal vein. 



Tributaries. — Its tributaries correspond to the branches of the artery. 



(a) The superior hemorrhoidal vein (v. haemorrhoidalis superior) has its origin from the 

 upper part of the hemorrhoidal ple.xus by several branches, and, passing upward, unites with the 

 sigmoid veins to form the inferior mesenteric. Through the hemorrhoidal plexus it communi- 

 cates with the middle and inferior hemorrhoidal veins, thus placing the portal and inferior caval 

 systems in communication. 



{d) The sigmoid veins (vv. sigmoideae) are variable in number and pass from the sigmoid 

 flexure and the lower portion of the descending colon to the inferior mesenteric, the lowest one 

 uniting with the superior hemorrhoidal to form that vein. 



