CHAPTEK XXVII 



THE ALIMENTARY CANAL 



THE alimentary canal consists of a long muscular tube lined by 

 mucous membrane beginning at the mouth, and terminating at the 

 anus. It comprises the mouth, pharynx, oesophagus, stomach, small 

 intestine and large intestine. Opening into it are numerous glands 

 which pour juices into it; these bring about the digestion of the food 

 as it passes along. Some of the glands, like the gastric and intestinal 

 glands, are situated in the lining mucous membrane of the canal; 

 others, like the salivary glands, liver, and pancreas, are situated at a 

 distance from the main canal, and pour their secretion into it by 

 means of side tubes or ducts. 



THE MOUTH 



This cavity is lined by a mucous membrane consisting of a corium 

 of fibrous tissue with numerous patches of lymphoid tissue in it, 

 especially in the posterior regions ; and an epithelium of the stratified 

 variety closely resembling the epidermis. The surface layers, like 

 those of the epidermis, are made of horny scales. Opening into the 

 mouth are a large number of little mucous glands, and the salivary 

 glands pour their secretion into the mouth also. The teeth (p. 64) 

 have been previously studied. The tongue will be considered later 

 in connection with taste. 



THE PHARYNX 



That portion of the alimentary canal which intervenes between 

 the mouth and the oesophagus is termed the Pharynx. It is con- 

 structed of a series of three muscles with striated fibres (constrictors), 

 which are covered by a thin fascia externally, and are lined internally 

 by a strong fascia (pharyngeal aponeurosis), on the inner aspect of 

 which is areolar (submucous) tissue and mucous membrane, con- 

 tinuous with that of the mouth, and, as regards the part concerned 

 in swallowing, identical with it in general structure. The epithelium 

 of this part of the pharynx, like that of the mouth, is stratified. 



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