240 



CHORDATE ANATOMY 



Secretions pass from each lateral lobe by a single duct, the two uniting 

 to form the hepatic duct. Nearer the intestine, the hepatic duct joins the 

 cystic duct from the gall bladder to form the common bile duct or ductus 

 choledochus, which opens into the duodenum at a point about three or 

 four inches from the pylorus. 



The liver is a compound tubular gland, the tubules of which are 

 arranged radially around branches of the hepatic vein. Each cluster of 

 tubules around a central intralobular vein forms a lobule. (Fig. 225) 

 The numerous lobules of the Hver are bound together by interlobular 

 connective tissue containing interlobular veins which are branches of the 



POST CAVA VEIN 



CUT EDGE OF 

 PERITONEUM 



HEPATIC 

 ARTERY 



RIGHT LOBE 



QUADRATE LOBE/ 



GALL BLADDER/ \BILE DUCT 



Fig. 224. — The human liver viewed from below. (Redrawn after Sobotta.) 



portal vein, interlobular ducts carrying bile, and branches of the hepatic 

 artery. Connexions between intralobular and interlobular veins are 

 effected by means of intralobular capillaries or sinusoids, which bathe 

 the liver tubules and supply them with the materials for secreting the bile. 

 The relations may best be understood by examination of the diagram 

 (Fig. 226). While branches of the vagus nerve reach the liver, most of its 

 nerves belong to the sympathetic system. 



The gall bladder is a pear-shaped muscular sac between three and four 

 inches in length, holding about 30 cc. Its inner surface is lined by a 

 mucous epithelium which is thrown into folds. Crescentic folds in the 

 neck of the bladder and in the common bile duct form a sort of spiral 

 valve. When food enters the duodenum from the stomach, the muscles of 

 the gall bladder squeeze the bile into the intestine. 



Development of the Liver. The anlage of the liver appears in a 

 2.5 mm. human embryo as a ventral outpocketing of the fore-gut near the 

 anterior intestinal portal, between the two vitelline veins. See Fig. 217. 



