136 TOPOGRAPHIC AND APPLIED ANATOMY. 



PLATE 17. 



The position of the pylorus, cardia, large intestine, and spleen of a fifteen-year-old girl. A deeper layer of the 

 model of Plate 16. 



61). This vessel supplies all of the small intestine and a considerable portion of the large in- 

 testine. Its branches are: 



1 . The inferior pancreaticoduodenalis, to the duodenum and the head of the pancreas ; 



2. The vasa intestini tenuis (arteria intestinales), about fifteen in number, running in the 

 mesentery to the intestinal coils; 



3. The ileocolic artery to the terminal portion of the ileum and to the commencement of 

 the ascending colon; 



4. The arteria colica dextra to the ascending colon; 



5. The arteria colica media to the transverse colon. 



This vessel consequently supplies that portion of the intestinal tract extending from 

 the duodenum to the splenic flexure of the colon. The intestine beyond this point is 

 supplied by the third single visceral artery, the inferior mesenteric (Plate 15), which arises 

 from the abdominal aorta at the level of the third lumbar vertebra. It runs behind the peri- 

 toneum and divides into two main branches: 



1. The arteria colica sinistra to the descending colon, and 



2. The superior hemorrhoidal artery to the rectum. The sigmoid arteries supply the 

 sigmoid colon. 



The portal vein is a very large venous trunk, only three centimeters in length, which enters 

 the liver at the transverse fissure. It receives the blood from that portion of the gastro- 

 intestinal tract which is situated between the cardia and the anus, from the pancreas, from 

 the spleen, and from the gall-bladder, and transmits it to the liver, from which it reaches the 

 inferior vena cava through the hepatic veins. It will be noted that the blood from the three 

 single visceral branches of the abdominal aorta passes into the inferior vena cava by an indirect 

 route through the liver, while the blood from the paired branches (visceral and parietal) emp- 

 ties directly into the inferior vena cava. The trunk of the portal vein lies in the hepato- 

 duodenal ligament (see pages 125-127) and arises behind the head of the pancreas by the 

 union of the splenic, the superior mesenteric, and the inferior mesenteric veins (Figs. 61 and 

 69). The important anastomoses of the portal system have been described upon page 122. 

 In the region of the portal vein there are more blood-vessels compressed into a comparatively 

 small space than in any other portion of the body (Fig. 61). 



The Large Intestine. The large intestine commences with the cecum and with the ver- 

 miform appendix (Plates 14 and 18), one of the most fertile regions of modern surgery. The 

 cecum lies in the right iliac fossa upon the iliac fascia and the iliacus muscle; it extends to 

 the left as far as the outer margin of the right psoas major muscle. Like the vermiform process, 

 it usually possesses a complete peritoneal reflection, and is consequently in contact with the 

 inner surface of the abdominal wall. In contrast to the ascending colon, it is a comparatively 

 movable portion of the intestine. The posterior peritoneal covering may be wanting, however, 

 and the cecum is then adherent to the iliac fossa. The vermiform process is usually freely 

 movable, being fixed only by its own mesenteriolum and partly covered by the cecum. . It may 



