1108 



THE DIGESTIVE SYSTEM. 



If, however, the tongue is raised, there is exposed a limited space to which the 

 term sublingual space is more usually applied (Fig. 876). 



The term " floor of the mouth," or sublingual region, is frequently applied to the muscular 

 and other structures, especially the mylo-hyoid muscles, which fill in the interval between the 

 two halves of the body of the mandible. These structures, with the hyoid bone, form the basis 

 upon which the tongue and the mucous membrane of the sublingual space are supported, and 

 they extend from the symphysis menti, in front, to the body of the hyoid bone, behind. 



The sublingual region (Fig. 876) is covered by the mucous membrane between 

 the deep surface of the gum and the inferior aspect of the tongue. When the tip 

 of the tongue is raised the membrane forms in the median plane a prominent fold, 



the frenulum linguae, stretching from 

 the floor of the mouth to the inferior 

 surface of the tongue. On each 

 side of the frenulum, near its 

 junction with the floor, there can 

 be readily made out a prominent 

 soft papilla, the caruncula sub- 

 lingualis, on which the opening of 

 the duct of the submaxillary gland 

 (O.T. Wharton's duct) may be seen 

 (Fig- 8l76 )- Kenning laterally and 

 posteriorly, on each side, from this, 

 - t L o a Ihowthe U gtnd Ut and occupying the greater part of 



i. Plica nmbriata th6 n ^\ { *** m Uth > ther6 ls a 



well-marked ridge, plica sublmguahs, 

 due to the projection of the under- 

 lying sublingual gland. Most of 

 the ducts of this gland open near 

 the crest of the ridge on each side. 

 ni u a c ryg f iand submax ' There is also another fold, called 

 openings of ducts of the plica fimbriata, medial to each of 



the submaxillary , , . . 



the others, on the inferior surface 



The philtrum 



fongue r gland f 



Frenulum linguae 



gland 

 Sublingual gland 



of the tongue. 





Plica sublingualis, 

 v with openings of 

 ducts of sublingual 

 gland 



FIG. 



876. OPEN MOUTH WITH TONGUE RAISED, AND THE 

 SUBLINGUAL AND ANTERIOR GLANDS EXPOSED. 



When the mouth is closed, and re- 

 spiration is carried on through the nose, 

 the cavum oris is reduced to a slit-like 

 space, and practically obliterated by the 

 tongue coming in contact with the palate 

 above, and with the gums and teeth 

 laterally and in front. When the 



The sublingual gland of the left side has been laid bare by the mou j ih . is sli g htlv P en and th . e teeth 

 removal of the mucous membrane ; to expose the anterior nearly in contact, the tongue becomes 

 lingual gland of the right side a thin layer of muscle, in somewhat concave or grooved along tJ 

 addition to the mucous membrane, has been removed. A median plane, and leaves a channel-like 

 branch of the lingual nerve is seen running on the medial space between it and the palate, while it 

 aspect of the gland. The profunda vein also is faintly remains in contact with the roof and 

 indicated on this side. gums laterally. By depressing the hyoid 



bone together with the root of the tongue, 



the cavum oris can be increased to a considerable size even when the teeth are in contact. Finally, 

 by the simultaneous descent of the mandible and hyoid bone with the tongue, and the ascent of 

 the soft palate, the cavity is increased to its greatest dimensions (Fig. 874). 



Labia Oris. The lips are the two movable folds, covered superficially by skin, 

 and on their deep surface by mucous membrane, which surround the rima oris. The 

 meeting of the lips at each side constitutes the commissure, and bounds the 

 angle of the mouth (angulus oris). Laterally, they are prolonged into the cheeks, 

 with which they are continuous. The junction of the lips and cheek is marked 

 on the surface by the sulcus naso-labialis, which passes downwards and laterally 

 from the margin of the nose towards the angle of the mouth, while the sulcus 

 mento-labialis separates the lower lip from the chin. The upper lip presents on 

 its superficial surface a well-marked vertical groove, the philtrum, bounded by two 

 distinct ridges descending from the columella nasi (Fig. 876) ; inferiorly the groove 



