220 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



artery which passes to the walls of the anterior part of the stomach and a pos- 

 terior gastric artery which runs posteriorly in the gastrohepatic ligament where 

 it branches to both limbs of the stomach. The posterior gastric artery near its 

 origin from the coeliac sends about two hepatic arteries to the liver. The 

 pancreatico-mesenteric artery sends pancreatic branches into the pancreas, a 

 large duodenal branch into the duodenum, a posterior gastrosplenic artery which 

 runs posteriorly along the narrowed part of the spleen and adjacent stomach 

 wall, and a large anterior mesenteric artery which passes along the right side of 

 the small intestine and branches at the lines of attachment of the spiral valve. 

 Shortly posterior to the point of origin of the coeliac artery two arteries arise 

 from the dorsal aorta. They are the gastrosplenic and the superior mesenteric. 

 The gastrosplenic proceeds to the thick portion of the spleen and the adjacent 

 stomach wall. The superior mesenteric supplies branches to the gonads and 

 then, as the posterior mesenteric artery, passes along the left side of the small 

 intestine, branching at the lines of attachment of the coils of the spiral valve. 

 The dorsal aorta proceeds unbranched for some distance and then gives off the 

 inferior mesenteric artery. This passes into the adjacent gonads to which it 

 supplies some branches and then emerging from the gonad proceeds to the rectal 

 gland where it forms a network of branches. 



Skate: Shortly after entering the pleuroperitoneal cavity, the dorsal aorta 

 gives off the coeliac artery, which supplies a number of organs. It has: a hepatic 

 branch to the liver; an anterior gastric branch which divides into dorsal and 

 ventral gastric arteries to the stomach wall; splenic branches to the spleen; 

 and a gastroduodenal branch, from which arise a posterior gastric artery to the 

 posterior part of the stomach, pancreatic branches to the pancreas, and a duodenal 

 branch to the pylorus and duodenum. Shortly posterior to the origin of the 

 coeliac artery, the dorsal aorta gives rise to the superior mesenteric artery, which 

 after some small branches to the pancreas and spleen proceeds posteriorly along 

 the small intestine to which it supplies branches at the lines of attachment of 

 the turns of the spiral valve. Shortly caudad of the origin of the superior 

 mesenteric artery, the inferior mesenteric artery branches from the dorsal aorta. 

 It sends genital arteries to the gonads and their ducts and then passes in the 

 mesentery to the rectal gland. 



The lateral visceral and somatic branches of the dorsal aorta are similar in 

 the three forms under consideration. The former consist of the genital arteries 

 already noted (but completely developed only in mature specimens) and the 

 renal arteries into the kidneys. The latter are seen by loosening the kidney from 

 the dorsal body wall and looking on the dorsal surface of the organ. The somatic 

 branches consist of paired parietal arteries to the body wall, passing out along 

 the myosepta. The arteries to the paired fins are merely enlarged parietal 

 vessels. The subclavian to the pectoral fin was already seen. The paired 

 iliac arteries to the pelvic fins arise from the dorsal aorta shortly in front of 



