THE ALIMENTARY CANAL. 221 



sheets which bound this area constitute the coronary hgament 

 of the hver. This Hgament is broader where it passes from the 

 left hiteral lobe to the diaphragm and is called the triangular 

 ligament. (There is perhaps a corresponding right trangular 

 ligament, from the cranial division of the right lateral lobe.) 

 The caudal division of the right lateral lobe is held to the 

 kidney of that side by the hepatorenal ligament. 



II. THE ALIMENTARY CANAL. APPARATUS DIGESTORIUS. 



The alimentary canal may be divided into mouth, pharynx, 

 oesophagus, stomach, small intestine, and large intestine. 

 With these are associated certain accessory structures, — the 

 salivary glands, the Hver, and the pancreas. The spleen, 

 though not belonging to the digestive system, is usually 

 described in connection with it. The respiratory organs are 

 almost throughout in close relation with the organs of the 

 digestive system. 



I . The Mouth. Cavum oris. — The mouth cavity extends 

 from the lips to the pharynx. It is narrower toward the lips, 

 broadens caudad as far back as the last teeth, then becomes 

 narrowed to form the isthmus faucium, by which it communi- 

 cates with the pharynx. The mouth cavity is divisible into 

 the vestibule of the mouth (vestibulum oris), which comprises 

 that part outside the jaws proper, bounded externally by the 

 lips and cheeks, and the mouth cavity proper (cavum oris 

 proprium), which lies within the teeth. That portion of the 

 vestibule which is bounded by the cheeks is sometimes farther 

 distinguished as the buccal cavity. The entire mouth cavity 

 (except the teeth) is lined by the mucous membrane or mucosa. 



The lips (labia oris) are thick folds of skin bounding the 

 entrance to the mouth cavity. The outer surface is covered 

 with hair; the inner surface is covered with the mucous mem- 

 brane. The upper lip is marked in the median line by a deep 

 external groove which extends upward to the septum of the 

 nose. Along the inner surface of this groove the lip is closely 

 united to the jaw by a thick fold, the frenulum of the upper 

 lip. For some distance on each side of the frenulum the inner 



