THE ABDOMINAL CAVITY 279 



reflected forwards on to the liver. The inferior layer passes 

 downwards and forms a complete covering to the posterior 

 abdominal wall below the pancreas. Along a line passing 

 obliquely downwards and to the right, it 'is lifted off the wall 

 to form the mesentery, which encloses the jejunum and ileum. 

 After covering the pelvic viscera (p. 357), this layer passes 

 upwards on the anterior abdominal wall. 



It will be seen from Fig. 85 that a portion of the peritoneal 

 cavity is shut off behind the stomach. This is the Omental 

 Bursa (Lesser Sac). It is a developmental diverticulum 

 (p. 303) of the great sac, with which it communicates through 

 a single opening, the epiploic foramen (of Winslow). 



The Greater Omentum forms a protective covering over 

 the abdominal viscera below the level of the stomach. It 

 contains a variable amount of fat, and is usually the first structure 

 seen when the abdomen is opened. The lower and the lateral 

 margins are free, and it can therefore be easily moved about 

 in abdominal operations. In addition, the greater omentum 

 wanders to any region of the abdomen where inflammatory pro- 

 cesses exist, and the surrounding adhesions which it forms are of 

 great value in limiting the spread of infection. On this account 

 it has been termed by Morison the "policeman of the abdomen." 



The Lesser Omentum passes from the lesser curvature of 

 the stomach and the corresponding border of the first inch and 

 a half of the duodenum to the porta (transverse fissure) of the 

 liver. The two layers of which it consists are closely applied 

 to one another, and form a thin, transparent sheet, save near 

 the right border where they are separated by the portal vein, 

 bile-duct, and hepatic artery. Round this border, which is 

 free and unattached, the two layers become continuous (Fig. 86). 

 Occasionally the lesser omentum is continued beyond the vessels 

 and duct, and receives attachment to the inferior surface of the 

 gall-bladder. Its free border may then be traced downwards 

 over the duodenum to the transverse colon, and on this account 

 the additional part is called the hepato-colic ligament. It 

 contains no vessels of any size, but the gall-bladder lies within 

 its upper attachment. It may be cut through parallel to the 

 gall bladder in exploring the epiploic foramen. 



The Epiploic Foramen (of Winslow) lies behind the right 

 free border of the lesser omentum. It is bounded above by the 

 liver (caudate lobe), and behind by the peritoneum which covers 

 the inferior vena cava. Below it is limited by the first part of 



18 b 



