242 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



veins opening directly into the right auricle. There are three of these veins, the 

 two precavals and the postcavaL The postcaval enters the right auricle from 

 behind, emerging from the liver. The precavals come from the anterior part 

 of the body, one on each side, and curving toward the heart at the level of the 

 auricles enter the right auricle. The pulmonary veins may be noticed opening 

 into the left auricle. 



2. The hepatic portal system. Turn to the peritoneal cavity. Cut across 

 the falciform ligament of the liver near the gizzard, noting first the small vein pass- 

 ing from the ventral ligament of the gizzard in the falciform ligament to the 

 liver. The lobes of the liver may now be turned forward. Running along the 

 dorsal surface of the liver and branching into its substance is the large hepatic 

 portal vein. The main part of the vein enters the right lobe of the liver, coursing 

 between the two bile ducts. The remainder of it lies along the dorsal surface 

 of the left lobe of the liver, sending branches into the liver, and at the left receives 

 the left and median gastric veins from the margin and left side of the gizzard and 

 from the proventriculus. Follow posteriorly that part of the hepatic portal 

 which lies between the two bile ducts. It is soon seen to be formed by the union 

 of three veins, a superior mesenteric, a gastroduodenal, and an inferior mesenteric. 

 The superior mesenteric collects from the greater part of the small intestine. The 

 gastroduodenal receives the right gastric vein from the right side of the gizzard; 

 the pancreatico-duodenal vein, which runs along the duodenal loop collecting from 

 duodenum and pancreas; and the mesenteric vein from the last loop of the small 

 intestine. The inferior mesenteric vein runs along the large intestine from which 

 it collects many branches. At its posterior end it turns dorsally and joins the 

 renal portal system, where it will be followed later. 



Draw the branches of the hepatic portal system. 



3. The systemic veins. As already stated, these consist of two precavals 

 and one postcaval. 



a) The branches of the precaval veins: As both veins have identical branches, 

 only one need be followed. Find the vein on each side lateral to the auricle and 

 trace each into the right auricle, lifting the heart. The left precaval passes 

 around the left auricle to enter the right auricle. The right precaval is much 

 shorter and enters the right auricle directly. 



Follow one precaval forward. It lies just posterior to a large artery and is 

 there seen to be formed by the union of three large veins, laterally the pectoral 

 vein, slightly anterior and dorsal to this the subclavian vein, and anteriorly the 

 jugular vein. Each of these veins should be followed. The pectoral vein at its 

 union with the others receives the internal mammary vein, ascending from the 

 inner surface of the ribs, and has also a tributary from the sternum and coracoid. 

 The main vein is formed laterally by the union of two veins emerging from the 

 pectoral muscles. These may be followed into the muscles from which they are 

 seen to collect many branches. The subclavian vein passes deep dorsally ventral 



