PHYSIOLOGY OF DIGESTION. 



THE MOUTH AND ITS GLANDS. 



The mucous membrane of the mouth contains sebaceous glands at the red 

 edge of the lips. It consists of fibrillar connective tissue intermixed with fine 

 elastic fibers. Toward the free surface it forms papillae, of which the largest 

 (0.5 mm.) are found on the lips and the gums, including some with double 

 points twin papillae. The smallest are on the palate and in the fold-like duplica- 

 tures of the mucosa. The submucous tissue, which passes directly over into the 

 mucosa, is thickest and most dense where the mucous membrane is immovably 

 attached to the periosteum of the maxilla and the palate, and also in the vicinity 

 of glandular involutions; while it is most delicate over movable and folded parts. 



The surface is lined by stratified nucleated 

 squamous epithelium (Fig. 92, 8), and it is, as a 

 rule, strongest and consists of the largest 

 number of layers in regions where the papillae 

 are longest. A diplosoma is found in the 

 deeper cells of the surface of the tongue. 



All of the glands of the mouth, in- 

 cluding the salivary glands, are divided, 

 with reference to their secretion, into 

 three groups: (i) albuminous or serous 

 glands, whose secretion contains albumin; 

 (2) mucous glands, whose ropy secretion 

 contains mucin, together with some albu- 

 min; (3) mixed glands, whose acini secrete 

 partly albumin and partly mucin, as, for 

 example, the submaxillary gland in man. 

 For a description of their structure refer- 

 ence may be made to page 258. 



Numerous mucous glands termed buccal, 

 palatine, lingual or molar muciparous glands, in 

 accordance with the region in which they occur 

 are present in the tissue of the mucosa, their 

 bodies appearing macroscopically as tiny white 

 nodules. They represent the type of simple branched tubular glands. The con- 

 tents of their secreting cells are partly mucus, which is expelled at the time of 

 secretion. The excretory duct, formed of connective and elastic tissues, with 

 a narrow outlet, is lined by a single layer of cylindrical epithelium. One duct 

 often receives that of a neighboring gland. The labial glands are mixed glands. 



The small glands of the tongue deserve special consideration. Two morpho- 

 logically and physiologically distinct glands can be distinguished, namely (i) 

 mucous glands (E. H. Weber's glands), situated especially near the root of the 

 tongue; compound alveolar glands, with bright, transparent, secreting cells and 

 mural nuclei, and a rather thick membrana prbpria; and (2) serous glands (von 

 Ebner's glands) , situated about the circumvallate papillae (and the foliate papillae 

 in animals), and consisting of convoluted and branched tubules, characterized by 

 small, narrow cells, filled with droplets of secretion, containing a centrosome and 

 yielding an albuminous secretion. Halfwav up between the cells the intercellular 

 secretory ducts are found. (3) The Blandin-Nuhn glands, within the tip of the 

 tongue, consist of glandular lobules secreting mucus and saliva, and are, therefore, 

 mixed glands. Delicate varicose nerve-fibers pass up to the cells. 



256 



FIG. 93. Section through Lymph-folli- 

 cles of the Root of the Tongue 

 (after Schenk): B, lymph-follicles; 

 V, depression; A, adenoid connec- 

 tive tissue; S, mucous glands; E, 

 epithelium. 



