242 LABORATORY MANUAL FOR VERTEBRATE ANATOMY 



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

 two precavals and the postcaval. The postcaval enters the right auricle froi 

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

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

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

 into the left auricle. 



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

 the falciform ligament of the liver near the gizzard, noting first the small vein pas: 

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

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

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

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

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

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

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

 from the proven triculus. Follow posteriorly that part of the hepatic porta 

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

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

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

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

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

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

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

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

 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 precaval 

 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 am 

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

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

 shorter and enters the right auricle directly. 



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

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

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

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

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

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

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

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

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



