154 



NORMAL HISTOLOGY. 



FIG. 187. 



papillae. The papillae are of three kinds : the filiform or conical, 

 the fungiform, and the circumvallate. 



The conical papillae are widely distributed, occurring on all parts 



of the upper surface of the 

 tongue. They consist of a 

 conical or cylindrical elevation 

 of the connective tissue of the 

 mucosa, .5-2.5 mm. in height, 

 covered with a thick layer of 

 epithelium, the cells of which, 

 as the most exposed part of the 

 papillae, are partially removed 

 by abrasion, the remaining epi- 

 thelium presenting a ragged sur- 

 face. 



The fungiform papillae are 

 likewise found on all parts of 

 the tongue, but they are fewer 

 in number, lower, and broader 

 than the conical, appearing as 

 isolated but distinct red points. 

 The connective-tissue stalks of 

 these papillae are composed of a 

 dense felt-work of fibrous tissue, 

 and bear secondary papillae on 

 their upper surface, the epithelium completely enveloping the entire 

 connective-tissue core. 



The circumvallate papillae, usually eight to ten in number, are 



placed in two rows forming a A 

 at the posterior part of the dorsum 

 of the tongue. Each consists of 

 a large flattened fungiform papilla 

 surrounded by a deep furrow and 

 a secondary encircling ridge or 

 wall an arrangement which has 

 suggested the name. The upper 

 surface of the mucosa is beset 

 with minute secondary elevations, 

 which, however, are not apparent 

 on the free surface, being hidden 

 by the thick stratum of covering 

 epithelium. 



Lying altogether within the epithelium lining the sides of the deep 

 circular furrow, the taste -buds appear as inconspicuous oval bodies 



Section of human tongue showing conical papillae: 

 a, connective tissue of mucosa, which forms core of 

 papillae; b, 6, partially abraded epithelium; c.masses 

 of epithelial cells filling interpapillary recesses. 



FIG. 188. 



Section of tongue of child, showing a fungiform 

 papilla; the connective-tissue stroma is covered 

 by the epithelium. 



