Organs of Digestion. 



THE Apparatus for Digestion of the food consists of the alimentary canal, 

 and of certain accessory organs. 



The Alimentary Canal is a musculo-membranous tube, about thirty feet in 

 length, extending from the mouth to the anus, and lined throughout its entire 

 extent by mucous membrane. It has received different names in the various 

 parts of its course : at its commencement, the mouth, we find provision made 

 for the mechanical division of the food (mastication), and for its admixture with 

 a fluid secreted by the salivary glands (insalivation) ; beyond this are the organs 

 of deglutition, the pharynx and the oesophagus, which convey the food into that 

 part of the alimentary canal (the stomach) in which the principal chemical 

 changes occur; in the stomach, the reduction and solution of the food take 

 place ; in the small intestines, the nutritive principles of the food (the chyle), 

 by its admixture with the bile and pancreatic fluid, are separated from that 

 portion which passes into the large intestine, most of which is expelled from 

 the system. 



Alimentary Canal. 



{Duodenum. 

 Jejunum. 

 Ileum. 



(Esophagus. ( Cascum. 



Stomach. Large intestine < Colon. 



( Rectum. 



Accessory Organs. 

 Teeth. 



( Parotid. Liver. 



Salivary glands < Submaxillary. Pancreas. 



( Sublingual. Spleen. 



THE MOUTH. 



The Mouth (Fig. 384) is placed at the commencement of the alimentary canal ; 

 it is a nearly oval-shaped cavity, in which the mastication of the food takes 

 place. It is bounded, in front by the lips ; laterally, by the cheeks and the 

 alveolar processes of the upper and lower jaw ; above, by the hard palate and 

 teeth of the upper jaw ; below, by the tongue, and by the mucous membrane 

 stretched between the under surface of that organ and the inner surface of the 

 jaws, and by the teeth of the lower jaw ; behind, by the soft palate and fauces. 



The mucous membrane lining the mouth, is continuous with the integument 

 at the free margin of the lips, and with the mucous lining of the fauces behind ; 

 it is of a rose-pink tinge during life, and very thick where it covers the hard 

 parts bounding the cavity. 



The Lips are two fleshy folds, which surround the orifice of the mouth, formed 

 externally of integument, and internally of mucous membrane, between which 

 is found the Orbicularis Oris muscle, the coronary vessels, some nerves, areolar 

 tissue, and fat, and numerous small labial glands. The inner surface of each 

 lip is connected in the middle line to the gum of the corresponding jaw by a 

 fold of mucous membrane, thefrsenum labii superioris and inferioris, the former 

 being the larger of the two. 



The labial glands are situated between the mucous membrane and the Orbi 



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