THE DIGESTIVE SYSTEM 
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tubular form of the pyloric region; the pyloric sphincter muscle 
guarding the exit into the intestine; the muscular walls, and the 
deviation from the strict longitudinal and circular arrangement of 
muscle fibers thus giving rise to oblique layers; the character of its 
mucous lining with the numerous folds, an accommodation to the 
distensibility of the organ. 
Liver. —Note its location, voluminous size, and the form and 
arrangement of its lobes; the folds of the peritoneum supporting 
the liver and attaching it to the diaphragm (falciform ligament); 
the lesser omentum stretching between the liver, and the pyloric 
end of the stomach and anterior end of the intestine; the position 
of the gall bladder with ducts leading into it from the liver and the 
cystic duct leading from it into the anterior region of the intestine 
(duodenum). 
Pancreas. —Note its thin and irregular form due to its location 
within the mesentery between the stomach and duodenum, into 
which its duct leads. 
Small Intestine. —Note its length, involving convolutions and 
an enormous expansion of the ventral edge of the mesentery which 
supports it; the numerous blood vessels, lymph glands and vessels, 
fat deposits, and (especially conspicuous in the cat) small glisten¬ 
ing Pacinian corpuscles between the two layers of the mesentery; 
the muscular coats strongly differentiated into the longitudinal 
and circular layers; the velvety appearance of the mucous lining 
due to the villi which thickly stud its surface; the circular folds 
(valvulae conniventes) of the mucous lining; the differentiation 
of the first loop of the intestine as the duodenum, and the relation 
of this to the pancreas and its duct as well as to the cystic duct; 
the opening of the small intestine into the side of the large intestine 
(location of ileo-colic valve). 
Large Intestine. —Note its wider caliber; the blind end 
(caecum) extending beyond the opening of the small intestine 
into it (cf. the voluminous caecum of rodents, and the reduced 
caecum and the vermiform appendix of man); its differentiation, 
less clearly marked than in man, into ascending (right side), 
transverse, and descending colons, and rectum; thinner nature of 
the muscular walls, as compared with those of the small intestine, 
the absence of villi, and the smoother nature of the lining. 
