THE STOMACH 417 



The use of the term ligament in regard to the arrangement here is somewhat misleading, 

 smce the stomach is attached to the crus of the diaphragm by areolar tissue; the peritoneum 

 passes from the diaphragm to the stomach on each side of the area of adhesion. In soft material 

 there is the appearance of a ligament composed of two layers of peritoneum, but this is an artefact. 



2. The lesser omentum (Omentum minus) connects the lesser curvature and 

 the first part of the duodenum with the hver below the oesophageal notch and the 

 portal fissure. 



The part of the omentum which extends from the liver to the stomach is designated the lig. 

 hepato-gastricum, and the remainder which goes to the duodenum as the Ug. hepato-duodenale. 



3. The gastro-splenic omentum (Lig. gastrolienale) passes from the left part 

 of the greater curvature to the hilus of the spleen; it is continuous ventrally with 

 the greater omentum. 



4. The greater omentum (Omentum majus) connects the ventral part of the 

 greater curvature and the first curve of the duodenum with the terminal part of the 

 great colon and the initial part of the small colon. It does not pass directly between 

 these parts but forms a large sac, which will be described later. 



5. The gastro-pancreatic fold (Plica gastropancreatica) extends from the left 

 sac above the cardia to the duodenum. It is attached dorsally to the liver and 

 vena cava, ventrally to the pancreas. 



The stomach of the equida is relatively small, its capacity varying from two 

 to four gallons (ca. 8 to 15 liters). 



The size, form, and position of the stomach are subject to considerable variation. \^'hen 

 the stomach is nearly empty, the saccus csecus contains only gas and is strongly contracted; the 

 middle part (physiological fundus) contains the ingesta and preserves its rounded character, 

 while the pyloric part is contracted. In this state coils of small intestine usually lie ventral to the 

 stomach and may separate it entirely from the colon. In exceptional cases, when the organ is 

 empty and contracted, even the pyloric end is to the left of the median plane. When distended, 

 the middle part settles down some four or five inches, pushing back coils of the small intestine 

 which may he between the greater curvature and the large colon, and also pushing to one side the left 

 dorsal part of the great colon ; the spleen, small colon, and small intestine are pushed back by the 

 distention of the left sac. When the stomach is moderately full, its most ventral part lies opposite 

 to the ninth intercostal space and tenth rib, about a handbreadth above the level of the left costal 

 arch. 



Structure. — The wall is composed of four coats — serous, muscular, submucous, 

 and mucous. The serous coat (Tunica serosa) covers the greater part of the organ 

 and is closely adherent to the muscular coat except at the curvatures. It partially 

 bridges over the lesser curvature, and covers here elastic tissue which assists in 

 retaining the bent form of the stomach. The peritoneal folds have been described. 

 The muscular coat (Tunica muscularis) consists of three incomplete layers, an 

 external of longitudinal, a middle of circular, and an internal of oblique fibers. The 

 layer of longitudinal fibers (Stratum longitudinale) is very thin and exists only 

 along the curvatures and at the antrum. It is not present on the saccus caecus, 

 -and about the middle of the greater curvature it is almost entirely replaced by 

 elastic fibers to the antrum pylori. At the lesser curvature it is continuous with the 

 longitudinal fibers of the oesophagus. On the antrum pylori it forms a well-de- 

 veloped complete layer which is separate from that of the curvatures. The layer 

 of circular fibers (Stratum circulare) exists only on the glandular part. At the 

 pyloric orifice it forms a thick ring — the pyloric sphincter (Sphincter pylori). 

 Another ring, the antral sphincter, is found at the left end of the antrum pylori. 

 The oblique fibers (Fibrse obfiquse) are arranged in coarse bundles in two layers. 

 The external stratum covers the left sac and is largely a continuation of the longi- 

 tudinal fibers of the oesophagus. The internal stratum is found also on the left 

 sac; it is continuous with the circular fibers of the oesophagus and stomach and 

 exchanges fibers -ndth the external oblique layer. It forms a remarkable loop 

 around the cardiac orifice, constituting a powerful cardiac sphincter (Sphincter 

 cardise). The submucous coat (Tela submucosa) is a layer of loose connective 

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