184 



THE ENTODERMAL CANAL AND ITS DERIVATIVES 



This mass, a network of solid trabecule, is the glandular portion of the liver. 



The primitive, hollow, hepatic diver- 

 t ^"T~», .,..- -. ticulum later differentiates into the 



gall-bladder and the large biliary 

 ducts. 



Referring to Figs. 83 and 176, it 

 will be seen that the liver anlage lies 

 between the vitelline veins and is in 

 close proximity to them laterally. 

 The veins send anastomosing 

 branches into the ventral mesen- 

 tery. The trabecular of the expand- 

 ing liver grow between and about 

 these venous plexuses, and the plex- 

 uses in turn make their way between 

 and around the liver cords. The 

 vitelline veins on their way to the 

 heart are thus surrounded by the 

 liver and largely subdivided into a 

 network of vessels termed sinusoids. 

 The endothelium of the sinusoids is closely applied to the cords of liver cells 

 which, in the early stages, con- 

 tain no bile capillaries ( Fig. 177). 

 For the transformation of the 

 vitelline veins into the portal 

 vein and for the relations of the 

 umbilical veins to the liver see 

 Chapter IX. 



The glandular portion of 

 the liver grows rapidly and in 

 embryos of 7 to 8 mm. is con- 

 nected with the primitive hepa- 

 tic diverticulum only by a single 

 cord of cells, the hepatic duct 

 (Fig. 178 A). That portion of 



the hepatic diverticulum distal to the hepatic duct is now differentiated into the 

 terminal solid gall-bladder and its cystic duct. Its proximal portion forms the 



Fig. 176. — The liver anlage of a 4 mm. human 

 embryo (Bremer). /;/., intestine; Pa., pancreas; 

 V.V., veins in contact with liver trabecule. 



Fig. 177. — The trabecule and sinusoids of the liver 

 in section, k.c, trabeculae of liver cells; 5;'., sinusoids 

 (after Minot). X 300. 



