1100 



DIGESTIVE SYSTEM 



THE MOUTH 



The oral cavity [cavum oris] represents the first segment of the alimentary 

 canal. Its walls are exceedingly specialised in structure, corresponding to its 

 manifold functions (mastication, insalivation, taste, speech, etc.). 



Boundaries. — The oral cavity communicates anteriorly with the exterior 

 through the transverse oral fissure [rima oris], and posteriorly with the pharynx 

 through the isthmus of the fauces [isthmus faucium]. The anterolateral walls 

 are formed by the flexible lips and cheeks. The roof is chiefly immovable and is 



Fig. 846. — Diagram of the Alimentary Canal. 



NASAL CAVITY 



PALATE 

 MOUTH CAVITY 



TONGUE 



NASAL PHARYNX 



BILE AND 

 PANCREATIC -1-% 

 DUCTS 



RIGHT COLIC 

 FLEXURE 



DUODENUM 



TilFT COUC 

 FLEIURE 



formecl by the upper jaw with the hard and soft palate. The movable floor is 

 tormed by the lower jaw and the tongue. 



Subdivisions.— The oral cavity is subdivided by the alveolar and dental 

 arches into an inner cavity, the oral cavity jmrper [cavum oris proprium], and an 

 outer vestibule [vestibulum oris] adjacent to the lips and cheeks (fig. 848). When 

 the upper and the lower teeth are in apposition, the vestibule communicates 



