Organs of Digestion. 



THE Apparatus for the 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, which comprises the mouth, we find every provision 

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

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

 pharynx and the oesophagus (the organs of deglutition), which convey the food 

 into the stomach, that part of the alimentary canal in which the principal chemi- 

 cal changes occur ; in that organ the reduction and solution of the food take place ; 

 by its admixture with the bile and pancreatic fluid, in the small intestines, the 

 nutritive principles of the food (the chyle) are separated from that portion which 

 passes into the large intestine, and which is expelled from the system. 



Mouth. 

 Pharynx. 

 (Esophagus. 

 Stomach. 



Alimentary Canal 

 Small intestine 



Large intestine 



Accessory Organs. 

 Teeth. 



{Parotid. 

 Subm axillary. 

 Sublingual. 



{Duodenum. 

 Jejunum. 

 Ileum. 

 {Caecum. 

 Colon. 

 Eectum. 



Liver. 



Pancreas. 



Spleen. 



The MOUTH (fig. 319) 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 alveolar process 

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

 jaw; below, by the tongue, the mucous membrane stretched between the under 

 surface of this 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 pink rose tinge during life, and very thick where it covers the hard parts 

 bounding this cavity. 



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

 externally of integument, internally of mucous membrane, between which are found 

 the Orbicularis oris muscle, the coronary vessels, some nerves, areolar tissue, 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 mem- 

 brane, the frsenum labii superioris and frsenum labii inferioris, the former being 

 the larger of the two. 



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



