1202 



THE ORGANS OF DIGESTION 



MOUTH 



The vestibule (vestibulum or is) is a slit-like space, bounded in front and later- 

 ally by the lips and cheeks; behind and internally by the gums and teeth. Above 

 and below it is limited by the reflection of the mucous membrane from the lips 

 and cheeks to the gum covering the upper and lower alveolar arch respectively. 

 It receives the secretion from the parotid, buccal, molar, and labial glands, and 

 communicates, when the jaws are closed, with the cavum oris by an aperture on 

 each side behind the wisdom teeth, and by narrow clefts between opposing teeth 

 (interdental spaces). 



The cavity of the mouth proper (cavum oris proprium) is bounded laterally 

 and in front by the alveolar arches with their contained teeth; behind, it communi- 

 cates with the pharynx by a constricted aperture termed the isthmus faucium. It 

 is roofed in by the hard and soft palate. The greater part of the floor is formed 

 by the tongue, the remainder being completed by the reflection of the mucous 



membrane from the sides,and under surface 

 of the tongue to the gum lining the inner 

 aspect of the mandible. It receives the 

 secretion from the submaxillary, sublingual, 

 and lingual glands. 



Floor of the Mouth. If the tongue be 

 lifted out of its resting-place, the true floor 

 of the mouth, or sublingual region, may be 

 examined. In the midline a fold of mucous 

 membrane, the frenum linguae, extends from 

 the under surface of the tongue to the floor. 

 On each side of the frenum is a papilla, the 

 caruncula sublingualis, on the summit of 

 which is the small orifice of the submaxillary 

 (Wharton's) duct. Extending backward 

 from these caruncles, between the tongue 

 and the alveolar arches on each side, is a 

 carunculated fold, the plica sublingualis, 

 which becomes lost posteriorly. The car- 

 unculated elevations, of variable number, 

 present the orifices of the sublingual ducts. 



SMALL 

 INTESTINE 



Structure. 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 pharynx behind; it is of a rose-pink tinge 

 during life, and very thick where it covers the hard 

 parts bounding the cavity. It is covered by strati- 



ANUS fi e d squamous epithelium. In the subepithelial 



FIG. 9i3.-Dia*ram of the alimentary tube and ^elastic tissue are seen many small accessory 

 its appendages. (Testut.) salivary glands. 



The Lips (labia oris) are two fleshy folds which surround the orifice of the mouth, 

 formed externally by integument and internally by mucous membrane, between 

 which are found the Orbicularis oris muscle (Fig. 293), the labial vessels, some 

 nerves (Fig. 442), areolar tissue, and fat, and numerous small labial glands. 

 The upper lip is called the labium superius; the lower lip is called the labium 

 inferius. 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, the frenulum 

 (frenulum labii superioris and frenulum labii inferioris), the upper being the larger 

 of the two. 



The labial glands (glandulae labiales (Fig. 442) are situated between the mucous 

 membrane and the Orbicularis oris muscle around the orifice of the mouth. They 



