1072 THE DIGESTIVE SYSTEM. 
jom the central or intralobular vein (Fig. 721). This runs down through the centre 
of the lobule (Fig. 720, A), and opens at its base into a sublobular vein. The sublobular 
veins, uniting and growing larger by 
constant additions, finally form the 
Liver lobules 
wea —& (,/ On hepatic veins, which open into the vena 
Ade cava. 
ah Hepatic Cells.—In the intervals be- 
Seas : tween the branches of the capillaries, 
running from the interlobular to the 
intralobular veins (Fig. 721), are placed 
the polygonal-shaped, epithelial, hepatic 
cells. Between the cells run the bile 
=) canaliculi (ductus biliferi) which, passing 
2 Sets pee out of the lobule (Fig. 721), join the 
Tena cava— =: a epatic A : Fy : 
ena cava fein interlobular bile-ducts (ductus inter- 
A C lobulares), and these uniting, finally end 
SEL AY in the hepatic ducts. 
ye NIG Hepatic 
Me SSN ACh /artery 
Hepatic 4 V WOO 
cells PORTAL VEIN y Q 
NG _ Glisson’s < 7 
ee capsule In man, the liver first appears as two 
DEVELOPMENT OF THE LIVER. 
Liss hollow outgrowths from the ventral wall 
S>=Bile-duct of the foregut, in the position of the 
future duodenum. These outgrowths, 
which are formed entirely of entoderm 
Fic. 720.—DIAGRAMS ILLUSTRATING THE Structure (hypoblast), pass forward and upward 
or Liver. into a mass of mesodermic tissue—called 
A, Arrangement of liver lobules around the sublobular by His the septum transversum—which 
branches of the hepatic vein ; B, Section of a portal lies in front of the foregut just below 
canal, showing its contained branches of the portal the heart. In addition to constituting 
vein, hepatic artery, and bile-duct, surrounded by a Re cedorn ere: heh themes aS 
prolongation of Glisson’s capsule. the mesodermic bed in which the liver is 
developed, this mass also forms the chief 
rudiment of the future diaphragm ; through it, too, pass the great foetal veins on their 
way to the heart. 
The two outgrowths give off numerous solid buds of endodermic cells—known as 
hepatic cylinders—which grow into the tissue of the septum transversum, and there 
Interlobular 
Hepatic 
, cells 
Veins Bile ducts 
Fira. 721.-—DIAGRAM illustrating the arrangement of the blood-vessels (on left), and of the hepatic cells and 
bile-ducts (on right) within a lobule of the liver. The first diagram shows the interlobular veins 
running around the outside of the lobule, and sending their capillaries into the lobule to join the central 
vein. In the second diagram the bile capillaries are seen, with the hepatic cells between them, 
radiating to the periphery of the lobule, where they join the interlobular bile-ducts. 
branch and anastomose freely with one another, forming a complicated network, the 
meshes of which are occupied by blood-vessels. From the sides of these primary hepatic 
cylinders come off secondary cell buds, which similarly branch and anastomose ; and this 
process is continued until the mass of the liver is formed. 
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