502 



THE PORTAL SYSTEM OF VEIN'S. 



and behind the pancreas, Avhere it joins with the splenic vein to form 

 the vena portce. 



Fig. 320. Fig. 320. — Diagramma- 



tic Outline of the 

 Portal Vein and its 



EELATIONTO THeLiVER, 



&c. (A. T.) A 



The liver is supposed 

 to be turned ujnvards so 

 as to present a portion of 

 its under surface. a, 

 gall-bladder ; b, square 

 lol)e ; c, left lobe ; 1, 

 trunk of the vena iwrtsd ; 

 2, great or superior me- 

 senteric vein ; 2', its 

 middle colic branch, form- 

 ing loops of communica- 

 tion between the right 

 and left colic veins ; 3, 

 intestinal branches ; + , 

 small pancreatico-duode- 

 iial branch ; 4, right 

 colic branch ; 5, ileo- 

 colic ; 6, coronary vein of 

 the stomach ; + + , right 

 gastro-epijiloic ; 7, sple- 

 nic vein ; /', its branches 

 to the spleen ; 7", its 

 branches to the stomach ; 

 8, inferior mesenteric 

 vein ; 9, left colic branch; 

 9', its communication 

 with the middle colic ; 

 10, sigmoid ; ]1, superior 

 ha?morrhoidal ; 12, the 

 riglit, and 13, the left 

 division of the vena portiB 

 in the transverse fissure 

 of the liver ; 14, the ob- 

 literated cord of the um- 

 bilical vein ; 15, the ob- 

 literated cord of the duc- 

 tus venosus ; 16, part of 

 vena cava inferior. 



The branches of 

 the inferior mesen- 

 teric vein correspond with the ramifications of the artery of the same 

 name. They commence at the lower part of the rectum in the hemorr- 

 hoidal plexus, and unite into a single vessel near the sigmoid flexure 

 of the colon. From this point the vein proceeds upwards and inwards 

 along the lumbar region, behind the peritoneum, crossing between tlie 

 transverse mesocolon and the spine, or farther to the'left, and then 

 passing beneath and behind the pancreas, it reaches the splenic vein 

 in which it terminates. 



Varieties. — In some cases the umbilical vein remains in some degi'ce pervious 

 from the point where it joins the left portal branch, up to the inner surface of 

 the rectus muscle, and is joined in the latter situation by a branch of the deep 

 epigastric vein, thus establishing- a communication between the external iliac 

 and portal veins. This communicating branch, according to Luschka. is noiTnal, 



