Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/80



Prepare now to study the contents of the abdominal cavity, that part of the coelom which lies posterior to the diaphragm. Slit the abdominal wall in the sagittal plane from the diaphragm posteriorly nearly to the external genital organs, which lie between the hind legs. Do not injure either the external or internal genital organs. Make an anterior and a posterior cut at right angles to this longitudinal incision, reflect the lateral flaps, exposing the digestive and reproductive systems lying in the abdominal cavity. Examine the mesenteries supporting the digestive organs, and observe their veins.

The portal system comprises the veins which carry to the liver the blood from the capillaries of the intestines, stomach, pancreas, and spleen. All the tributaries of this system converge to the portal vein which goes into the liver immediately ventral to the entrance of the inferior vena cava into that organ. Trace the ramifications of the portal system throughout the mesenteries of the stomach and intestines. Just before it enters the liver the portal vein receives the pancreatico-duodenal vein from the duodenum and pancreas, and the gastro-epiploic vein from the pancreas and greater curvature of the stomach. These two vessels unite and enter the portal vein by a common trunk. The portal vein is formed by the confluence of the gastro-splenic and superior mesenteric veins. The gastro-splenic is formed by the union of branches from the spleen, pancreas, and lesser curvature of the stomach. The superior