Abstract
The liver and the bile-passage of five Platanista whose body length ranged from 76 to 118 cm were observed macro- and microscopically, and were discussed in the light of comparative anatomy.
The liver of Platanista presents a wedge-like shape, consisting of right and left lobes, the tapering right lobe of which is directed caudad along the median line of the body. The ratio (%) of liver weight to body weight ranged from 1.3 to 2.7.
The liver has no pars nuda and is suspended from the diaphragm, chiefly by the dorsal ligament (consisting of the fusion of the upper and the lower layers of the coronary ligament in ordinary mammals), falciform ligament and partially by the lesser omentum.
The inferior vena cava enters the caudal end of the right lobe and passes through the liver, being completely embedded in its parenchyme. The terminal portion of the intrahepatic vena cava inferior and the continuing part of three main hepatic veins (intrahepatic venous sinus) dilate extremely and are supposed to regulate the blood circulation.
The microscopical structures of the liver of Platanista are quite similar to those of other mammals.
The extrahepatic bile-passage is wholly embedded in the pancreas. Since Platanista has no gall-bladder there is no part that could be called ductus choledochus, and the common hepatic duct takes the name of hepato-pancreatic duct, after receiving at least two pancreatic ducts. The glandular structures of the bile-passage can be found from the thick portion of the interlobular bile duct, and the nature of the gland is serous tubulo-alveolar.
The terminal portion of the hepato-pancreatic duct perforates the duodenal wall and dilates in the tela submucosa, forming the socalled‘duodenal pouch’ as a specialized form of Vater's ampulla. The microscopical structure of the pouch is basically the same as that of the duodenum, and the lamina propria ucosae is occupied with tubulo-alveolar serous glands. The function of the pouch is briefly discussed in relation to the Brunner's gland, which is reported to be lacking in the cetacea.
