THE ORGANS OF DIGESTION 



beyond the anterior border of the liver; the body (corpus vesicae felleae) and neck 

 (collum vesicae felleae} are directed upward and backward to the left. The neck 

 of the gall-bladder is on a slightly higher level than the lowest point of the gall- 

 bladder; thus the weight of the bile is away from rather than toward the outlet. 

 The upper surface of the gall-bladder is attached to the liver by connective tissue 

 and vessels. The under surface is covered by peritoneum, which is reflected on 

 to it from the surface of the liver. Occasionally the whole of the organ is invested 

 by the serous membrane, and is then connected to the liver by a kind of mesentery. 



Relations. The body of the gall-bladder is in relation, by its upper surface, with the liver, 

 to which it is connected by areolar tissue and vessels; by its under surface, with the commence- 

 ment of the transverse colon; and farther back, with the upper end of the descending portion 

 of the duodenum or sometimes with the pyloric end of the stomach or the first portion of the 

 duodenum. The fundus is completely invested by peritoneum; it is in relation, in front, with 

 the abdominal parietes, immediately below the ninth costal cartilage; behind, with the trans- 

 verse arch of the colon. The neck is narrow, and curves upon itself like the letter S; at its point 

 of connection with the cystic duct it presents a well-marked constriction. 



When the gall-bladder is distended with bile or filled with calculi, the fundus may be felt 

 through the abdominal parietes, especially in an emaciated subject ; the relations of this sac will 

 also serve to explain the occasional occurrence of abdominal biliary fistulse, through which biliary 

 calculi may pass out, and of the passage of calculi from the gall-bladder into the stomach, duo- 

 denum, or colon, which occasionally happens. 



Structure. The gall-bladder consists of three coats serofibrous, muscular, and mucous. 



The external or serofibrous coat (tunica serosa vesicae felleae) consists of white fibrous tissue 

 that surrounds the muscle coat; the fundus is completely covered by peritoneum, while the body 

 and neck are covered on their under surfaces only. 



The muscular coat (tunica muscularis vesicae felleae) is a thin but strong layer which forms 

 the framework of the sac, consisting of dense fibrous tissue which interlaces in all directions and 

 is mixed with plain muscle fibres which are disposed chiefly in a longitudinal direction, a few 

 running transversely. 



The internal or mucous coat (tunica mucosa vesicae felleae) is loosely connected with the 

 fibrous portion of the preceding coat. It is generally tinged with a yellowish-brown color, and 

 is everywhere elevated into minute rugae, by the union of which numerous meshes are formed, 

 the depressed intervening spaces having a polygonal outline. The meshes are smaller at the 

 fundus and neck, being most developed about the centre of the sac. Opposite the neck of the 

 gall-bladder the mucous membrane projects inward in the form of oblique ridges or folds, forming 

 a spiral valve (Fig. 1078). 



The mucous membrane is covered with columnar epithelium, and secretes an abundance of 

 thick viscid mucus; it is continuous through the hepatic duct with the mucous membrane lining 

 the ducts of the liver, and through the ductus communis choledochus with the mucous membrane 

 of the duodenum. Mucous glands may be found in this coat, as well as diffuse lymphoid tissue 

 and solitary follicles. 



The Cystic Duct (ductus cysticus). The cystic duct, the smallest of the three 

 biliary ducts, is about an inch and a half (3.75 cm.) in length. It passes obliquely 

 downward and to the left from the neck of the gall-bladder, and joins the hepatic 

 duct to form the common bile duct. It lies in the gastrohepatic omentum in 

 front of the portal vein, the hepatic artery lying to its left side. The mucous 

 membrane lining its interior is thrown into a series of crescentic folds, from five 

 to twelve in number, similar to those found in the neck of the gall-bladder. They 

 project into the duct in regular succession, and are directed obliquely around the 

 tube, presenting much the appearance of a continuous spiral valve (valvula 

 spiralis [Heisteri]) (Fig. 1078). When the duct is distended, the spaces between 

 the folds are dilated, so as to give to its exterior a twisted appearance. 



The common bile duct (ductus choledochus) (Figs. 1078 and 1079), the largest 

 of the three, is the common excretory duct of the liver and gall-bladder. It is 

 about three inches in length, is of the diameter of a goose-quill, and is formed by 

 the junction of the cystic and hepatic ducts. 



It descends along the right border of the lesser omentum behind the first por- 

 tion of the duodenum, in front of the portal vein, and to the right of the hepatic 



