358 



DIGESTIVE SYSTEM OF THE HORSE 



and sixteenth ribs and -the diaphragm/ It is related to the pancreas behind and 

 the base of the spleen externally. The right or pyloric extremity is much smaller 

 and is continuous with the duodenum, the junction being indicated by a marked 

 constriction. It hes on the liver, a little to the right of the median plane, and a 

 little lower than the cardiac opening. About two or three inches (ca. 5 to 8 cm.) 

 from the pylorus there is a constriction which marks off the antrum pylori from the 

 rest of the right sac. The oesophageal orifice or cardia is situated at the left ex- 

 tremity of the lesser curvature, but about eight to ten inches (ca. 20 to 25 cm.) 

 from the left extremity. The oesophagus joins the stomach very obliquely. The 

 opening is closed by the sphincter cardise and numerous folds of mucous membrane. 

 The pyloric orifice communicates with the duodenum. Its position is indicated 

 externally by a distinct constriction. Internally it presents a circular ridge pro- 

 duced by a ring of muscular tissue — 

 the sphincter pylori. 



The stomach is held in position 

 mainly by the pressure of the surround- 

 ing viscera and by the oesophagus. The 

 following peritoneal folds connect it 

 with the adjacent parts: 



1. The gastro-phrenic ligament 

 (Lig. gastrophrenicum) connects the 

 great curvature, from the cardia to 

 the left extremity, with the crura of 

 the diaphragm. This leaves a narrow 

 area uncovered with peritoneum, and 

 here the stomach is attached to the 

 diaphragm by loose connective tissue. 



2. The small or gastro-hepatic 

 omentum (Omentum minus) connects 

 the lesser curvature and the first part 

 of the duodenum w^th the liver below 

 the oesophageal notch and the portal 

 fissure. 



3. The gastro-splenic omentum 

 (Lig. gastro-lienale) passes from the 

 left part of the great curvature to the 

 hilus of the spleen. 



4. The great or gastro-coUc omen- 

 tum (Omentum majus) connects the 

 ventral part of the great curvature 



and the first curve of the duodenum Avith the terminal part of the great colon and 

 the initial part of the small colon. 



5. The gastro-pancreatic fold (Plica gastro-pancreatica) 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 equidse 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. When 

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

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

 while the pyloric portion is contracted. When distended the middle portion settles down some 

 four or five inches, pushing back coils of the small colon and small intestine which may lie between 

 the great cmrvature and the large colon, and also pushing to the left or right the left dorsal part of 



^ This is the position in the expiratory phase as usually seen in the dead subject. In inspira- 

 tion the saccus caecus lies under the upper parts of the sixteenth and seventeenth ribs. 



Fig. 260. — Everted Stomach op Horse from which 



THE Mucous MeMBR.ANE HAS BEEN REMOVED. 



O, CEsophagus; D, duodenum; h, circular layer; 

 c', internal oblique fibers; c", loop around cardia; c'" , 

 transition of internal to external oblique fibers; rf, fibers 

 connecting the two branches of the cardiac looij; p, 

 antral sphincter; p' , pyloric sphincter. (Ellenberger- 

 Baum, .\nat. d. Haustiere.) 



