THE INTESTINAL BLOOD-X'ESSELS 241 



the third Hmb of the caecum and the adjacent portion 

 of the ileum; anastomosing with (3). 



(7) A caecal artery to the second Hmb and the posterior 

 end of the third Hmb of the caecum. 



(8) Terminal branches to the parts of the ileum, caecum, 

 and colon about the sacculus rotundus; anastomosing 

 with (4). 



(d) The intestinal arteries (aa. intestinales), about twenty in 

 number, are given off from the superior mesenteric artery 

 after the ileocaecocolic artery has left it, and are distributed 

 to the free portion of the mesenterial small intestine. The 

 successive vessels are connected by anastomoses the first 

 connecting also with a branch of the inferior pancreat- 

 icoduodenal artery. All but two of the intestinal arteries 

 . arise from one side of the superior mesenteric artery, one 

 forms the end of the latter, and one springs from its opposite 

 side. The last anastomoses forward with a branch of the 

 appendicular artery. 



Locate in the descending mesocolon the inferior mesenteric 

 artery (a. mesenterica inferior), a small median vessel arising 

 from the abdominal aorta. It has two main branches — the 

 left colic artery (a. colica sinistra) to the anterior portion of 

 the descending colon (anastomosing with the middle colic), and 

 the superior haemorrhoidal artery (a. haemorrhoidalis superior) 

 to the posterior portion of the colon and the rectum, continuing 

 caudad along the dorsal surface of the latter. 



The superior mesenteric vein (v. mesenterica superior), the 

 chief tributary of the portal, collects the blood distributed by 

 the superior mesenteric artery, its tributaries being similar in 

 arrangement to the branches of the artery. The inferior 

 mesenteric vein (v. mesenterica inferior) collects blood from 

 the descending colon and rectum and joins the superior mesen- 

 teric vein to form the portal vein (p. 234). It may be traced 

 forward in the descending mesocolon, where it crosses the 

 inferior mesenteric artery almost at right angles, only its more 

 posterior part accompanying the arteries. 



