HISTOLOGY 



down from the epithelium, having ducts which open into the deep grooves 

 (Fig. 223). The foliate papillae are parallel folds of mucous membrane, 

 in the epithelium of which there are many taste buds. These structures, 

 which occur also in the lateral walls of the vallate papillae (Fig. 223), 

 will be described with the nerves of the tongue. 



The tunica propria of the mucous membrane is a loose connective 

 tissue layer containing fat. It is not sharply separated from the denser 

 submucosa. At the tip of the tongue, or apex lingua, and over the 

 dorsum, the submucosa is particularly firm and thick, forming the 

 fascia lingua. Three sorts of glands branch in the submucosa and 



Cornified epithelium. 



Secondary 



papillae of a 



fungiform 



papilla. 



Primary papilla. 



Oblique section 



of a filiform 



papilla. 



Secondary 



papillae of a 

 filiform' 

 papilla. 



Primary 

 papillae. 



Nerves. 



*m 



- -- ;^ : W$fc : 



Artery. 



FIG. 222. FROM A LONGITUDINAL SECTION OF THE HUMAN TONGUE. 

 x, Epithelium showing post-mortem disintegration. 



Fascia linguae. 



.... Striated mus- 

 cle fibers. 



X 25. 



may extend into the superficial part of the muscle layer. These are 

 the serous glands found near the vallate and foliate papillae; mucous 

 glands occurring at the root of the tongue, along its borders, and in 

 an area in front of the median vallate papilla; and the two mixed 

 anterior lingual glands, from half an inch to an inch long, each of which 

 empties by five or six ducts on the under surface of the apex. The 

 structure of these types of glands will be described in the section on 

 oral glands. 



The muscular layer consists of interwoven bundles of striated fibers 

 which are inserted into the submucosa or into the intermuscular connect- 



