360 



DIGESTIVE SYSTEM OF THE HORSE 



The mucous coat is clearly divided into two parts. That which lines the left 

 sac resembles the a^sophageal mucous membrane, and is termed oesophageal or 

 cuticular. It is white in color, destitute of glands, and covered with a thick, 

 squamous, stratified epithelium. At the cardiac orifice it presents numerous folds 

 which occlude the opening.^ It terminates abruptly at an elevated, denticulated, 

 sinuous line, termed the cuticular ridge (Margo plicatus). Below and to the right 

 of this line the mucous membrane has a totally different character, being soft 

 and velvety to the touch, and covered by a mucoid secretion. It is glandular, and 

 three zones may be recognized, although no sharp line of demarcation exists. A 

 narrow zone next to the cuticular ridge has a yellowish-gray color, and contains 

 short tubular cardiac glands (Cardiac gland region). Next to this is a large area 

 which has a mottled reddish-brown color, and contains fundus glands (fundus gland 



region). This part of the mucous 

 membrane is thick and very vascular, 

 and corresponds to the fundus of 

 the stomach in man and the dog. 

 The remainder of the mucous mem- 

 brane has a reddish-gray color and 

 contains branched, tubular, pyloric 

 glands (pyloric gland region); it cor- 

 responds to the pyloric portion of 

 man and the dog. 



The folding of the stomach wall 

 at the lesser curvature produces a 

 prominent ridge which projects into 

 the cavity of the stomach. Circular 

 ridges occur at the antral and pyloric 

 sphincters. 



Blood-vessels and Nerves. — The 

 stomach receives blood from all the 

 branches of the coeliac artery. The gastric veins drain into the portal vein. 

 The nerves are derived from the vagus and sympathetic nerves. 



Fig. 262. — Diagram of Zones op Mucous Membran 

 OF Stomach of Horse. 



THE SMALL INTESTINE 



The small intestine (Intestinum tenue) is the tube which connects the stomach 

 with the large intestine. It begins at the pylorus and terminates at the lesser 

 curvature of the csecum. Its average length is about seventy feet (ca. 22 meters). 

 When distended its diameter varies from two to four inches (5 to 10 cm.). Its 

 capacity is about twelve gallons (40 to 50 liters). 



It is clearly divisible into a fixed and a mesenteric or floating portion. The 

 fixed portion is termed the duodenum, while the mesenteric portion (Intestinum 

 tenue mesenteriale) is arbitrarily divided into parts termed the jejunum and ileum. ^ 



The duodenum is about three to four feet (ca. 1 to 1.25 m.) long. Its shape 

 is somewhat like a horseshoe, the convexity being directed toward the right. The 

 first part is directed to the right and forms an co -shaped curve. The convexity of 

 the first part of the curve is dorsal, of the second ventral. It lies on the middle 

 and right lobes of the liver, and presents two dilatations (Ampullae) with a constric- 

 tion between them. The duodenal angle or head of the pancreas lies in the con- 



' This 0(!clusion is usually so coinploto that (list out ion of the stomach by air or fluid forced 

 in through the pylorus may he carried far enough to rupture^ the stomach without ligating the 

 oesophagus. 



- No natural line of demarcation exists, but there is a marked increase of the thickness of 

 the wall toward the terminal part. Other differences will be noted in the further description. 



