ra 7 
1070 THE DIGESTIVE SYSTEM. 
two layers of the lesser omentum, with the portal vein behind and the hepatic artery 
to its left. It next descends behind the first part of the duodenum (Fie. s}), 
and then between the pancreas and descending duo- 
ADS. denum. Finally, it meets the pancreatic duct, and 
Oy the two, running together, pierce the inner wall of 
the descending duodenum very obliquely, and open 
-Bile-duet- by a common orifice on the bile papilla (papilla 
=pancreatie duodenalis), about 34 or 4 inches (8°7 to 10 em.) 
duet beyond the pylorus (see p- 1019). 
The length of the common bile-duct is about 3 inches 
(7am), and its diameter, which is very variable, is 
generally about + inch (6 to 7 mm.). 
Structure of Excretory Ducts.— With the exception 
of the peritoneal coat, which is absent, the hepatic, eystie, 
Fic. 719.—Dracram sHowine tHe 8d common bile-ducts, agree with the gall-bladder in 
BILE AND PANCREATIC DucTS general structure 
PIERCING THE WALL OF THE 
DUODENUM OBLIQUELY. The bile and pancreatic ducts, in piercing the wall of the 
ADS, Accessory pancreatic duct @uodenum, run obliquely through its coats for about 5 or ? of an 
(of Santorini); C, Circular mus- Inch (12 to 18 mi.), and, as a rule, do not unite until they have 
cular fibres; L, Longitudinal eee reached the opening on the bile papilla (Fig. 719). 
muscular fibres; M, Mucous This orifice is very much smaller than either duct, and the short 
coat. and relatively wide common cavity which precedes it is some- 
times known as the “ampulla of Vater.’ Occasionally the 
cystic and hepatic duets open into the duodenum separately. Sometimes, too, the cystic duct 
joins the right hepatic duct instead of the hepatic duct proper. 
VESSELS OF THE LIVER. 
The liver derives its blood-supply from two sources, namely —(1) the portal 
vein, which conveys to it, for further elaboration, the blood from the digestive system, 
laden with the products of digestion ; and (2) the hepatic artery, which supplies it with 
blood for the nourishment of its own tissue. All the blood is returned from the liver to 
the inferior vena cava by the hepatic veins. 
The portal vein and the hepatic artery pass up to the liver between the two layers 
of the lesser omentum and in front of the foramen of Winslow. Here they are accom- 
panied by the hepatic duct, which lies to the right, whilst the artery is placed to the 
left, and the portal vein behind both. In this order they enter the portal fissure, and 
there becoming re-arranged, so that the vein lies behind the artery in the middle and 
the duct in front, each breaks up into two chief branches—a right and a left—and several 
smaller ones, which enter the liver substance, surrounded by a prolongation of the con- 
nective tissue coat of the liver, known as Glisson’s capsule. Within the organ the three 
vessels run and divide together, so that every branch of the portal vein is accompanied 
by a corresponding (but much smaller r) branch of the hepatic artery and of the hepatic 
duct: and the three, surrounded by a prolongation of Glisson’s capsule, and accompanied 
by branches of the hepatic nerves and lymphatics, run in special tunnels of the liver 
substance, which are known as portal canals (Fig. 720, B). 
Finally, the portal vein breaks up into interlobular veins (ven interlobulares) which 
lie in the spaces between the liver lobules (Fig. 721). The branches of these enter the 
lobules on all sides, and unite with their capillary network, which converges towards 
the centre of the lobule, and joins the intralobular or central vein (vena centralis). 
The hepatic artery similarly divides into interlobular branches (rami arteriosi 
interlobulares) of a very small size, which accompany the interlobular branches of the 
vein, and supply the tissue and the vessels between the lobules. In addition, the hepatic 
artery gives off vaginal branches to supply the walls of the vessels and ducts, and the 
connective tissue in the portal canals; and capsular branches, which are distributed to 
the fibrous coat of the liver. 
The hepatic veins are two large and several small veins, which converge from the 
different portions of the liver (Fig. 720, A) to the vena cava. Their ultimate radicles are 
the intralobular or central veins, eh run down through the centre of the liver lobules, 
and passing out at the base, join the sublobular veins : these by their union finally form 
the hepatic veins. The two chief hepatic veins, which are of very large size, open into 
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