THE EXCRETORY APPARATUS OF THE LIVER 



1335 



^fc GALL-BLADDER 



artery (Fig. 984); it then passes between the head of the pancreas and descending 

 portion of the duodenum, and, running for a short distance along the right side 

 of the terminal part of the pancreatic duct, passes with it obliquely through the 

 wall of the descending portion of the duodenum between the mucous and muscular 

 coats in the submucous tissue for one-half to three-quarters of an inch (1.25 to 

 2 cm.). The two ducts usually unite just before opening into the duodenum 



(Figs. 1079 and 1080), but may remain 

 independent throughout (in about 10 per 

 cent, of individuals). The ampulla of 

 Vater (Fig. 1079) is the conical cavity 

 formed by the fusion of the two ducts, 

 and is much larger than the opening 

 on the bile papilla. It averages 3.9 mm. 

 in length. The average diameter of the 

 orifice is 2.5 mm. (Opie). The two ducts 

 open by a common orifice if there is an 

 ampulla, or by two separate orifices if 

 there is no ampulla, upon the summit of 

 a papilla, situated at the inner side of the 

 descending portion of the duodenum, a 

 little below its middle and about three or 

 four inches (7.5 to 10 cm.) below the 

 pylorus. Circular muscle fibres, contin- 



HEPATIC 

 DUCT 



DUCT Of 

 WIRSUNG 



PANCREATIC 

 DUCT 



AMPULLA 

 OF VATER 



WALL OF 



DUODENUM 



SPHINCTER OF 

 DUCT OF WIRSUNG 



COMMON 

 DUCT 



SPHINCTER OF 

 COMMON DUCT 



FIG. 1079. The biliary ducts. (Schematic.) 

 (Poirier and Charpy.) 



FIG. 1080. The sphincter of the common bile duct. 

 (Poirier and Charpy.) 



nous with the longitudinal fibres of the ducts, surround the termination of the 

 two ducts in the ampulla. These fibres constitute the so-called sphincter of Oddi 

 (Fig. 1080). 



Structure. The coats of the large biliary ducts are an external or fibrous, a middle or mus- 

 cular, and an internal or mucous. The fibrous coat is composed of strong fibroareolar tissue. 

 The muscular coat consists chiefly of circularly arranged smooth muscle tissue. The mucous 

 coat is continuous with the lining membrane of the hepatic ducts and gall-bladder, and also with 

 that of the duodenum; and, like the mucous membrane of these structures, its epithelium is of 

 the simple columnar variety. It is provided with numerous mucous glands, which are lobu- 

 lated and open by minute orifices scattered irregularly in the larger ducts. It is questionable 

 if the smallest biliary ducts, which lie in the interlobular spaces, have any coats. Heidenhain 

 thinks they have a connective-tissue coat, in which are muscle cells arranged both circularly and 

 longitudinally, and an epithelial layer, consisting of short columnar cells. 



Dimensions of the Bile Ducts. The hepatic duct is about two inches (5 cm.) in length, and 

 its lumen is one-sixth of an inch (4 mm.) in diameter. The cystic duct is about one and one- 

 half inches (3.75 cm.) in length, and its lumen is one-twelfth of an inch (2 mm.) in diameter. 

 The common duct is about three inches (7.5 cm.) in length, and its lumen is one-quarter of an 

 inch (6 mm.) in diameter. The duodenal opening is smaller than the common duct. The 

 ducts are capable of considerable distention, but the duodenal opening cannot be dilated (Hyrtl). 



Bloodvessels, Lymphatics, and Nerves of the Gall-bladder and Bile Ducts. The cystic 

 artery (Fig. 468), a branch from the right division of the hepatic, supplies the gall-bladder and 



