448 ABDOMEN 



structures lying on the posterior wall of the abdomen. The 

 contents of the greater omentum are (i) a portion of the 

 cavity of the omental bursa which separates the two anterior 

 from the two posterior layers; (2) between the two anterior 

 layers, along the lower border of the stomach, the right and 

 left gastro-epiploic blood vessels and their branches with lymph 

 vessels and small lymph glands ; (3) between the two posterior 

 layers small branches of the middle colic artery which have 

 crossed the surfaces of the transverse colon and are descending 

 into the lower border of the greater omentum where, in very 

 favourable circumstances, they anastomose with descending 

 branches of the gastro-epiploic arteries. 



Dissection. Clear away the anterior of the two anterior layers of the 

 greater omentum along the lower border of the stomach and expose the 

 gastro-epiploic arteries. Trace the left artery to the left to the gastro-lienal 

 ligament, and note that it passes forwards to the stomach between the two 

 layers of the ligament. At a later stage it will be followed to the splenic 

 artery from which it springs. Trace the right artery to the right to the 

 point where it springs from the gastro-duodenal artery at the lower border 

 of the first part of the duodenum. 



Remove the two anterior layers of the greater omentum (see Fig. 170). 

 This part of the dissection is not always easy to accomplish, for not un- 

 commonly the posterior of the two anterior layers is fused with the anterior 

 of the two posterior layers, the lower part of the cavity of the omental bursa 

 being obliterated ; but if the dissector commences near the left end of the 

 lower border of the stomach he will usually find the cavity persistent. First 

 he should pull the lower border of the stomach forwards and cut through 

 the two anterior layers of the omentum below the left gastro-epiploic artery ; 

 next he should introduce his fingers through the opening and gradually 

 separate the two anterior from the two posterior layers, then he must 

 enlarge the opening and after separating the anterior from the posterior 

 layers as far as possible he must cut away the anterior layers. After this 

 portion of the dissection is completed he must introduce one hand into the 

 cavity of the omental bursa and he will find that he can pass it upwards 

 behind the stomach and behind the posterior surface of the lesser omentum 

 to the liver. If now he turns his fingers to the right he will be able to pass 

 them behind the portal vein and through the epiploic foramen (Winslow) 

 into the great sac. He should note as he passes his hand upwards that the 

 cavity of the small sac is constricted, between the oesophagus above and to 

 the right and the pylorus below and to the left, by two folds of peritoneum 

 which pass forwards from the posterior wall of the abdomen to the 

 oesophagus and the pylorus respectively. He will find, at a later stage of 

 the dissection, that these folds are connected with the peritoneum on the 

 anterior surface of the pancreas ; they are therefore called the left and right 

 pancreatico-gastric folds. The left is produced by the left gastric artery as 

 it passes round the left border of the sac to gain entrance into the lesser 

 omentum, and the right is produced by the hepatic artery as it turns round 

 the right margin of the sac at the lower border of the epiploic foramen 

 (Winslow). 



Next remove the posterior layer of the lesser omentum and so open into 

 the upper part of the omental bursa, but take care not to injure the contents 



