i 7 8 



HISTOLOGY. 



Filiform ] 

 papilla. -, 



Secondary 

 . papillae. 



face of the tongue is free from epithelial papillae; its mucosa resembles 

 that which lines the mouth. The posterior part of the tongue contains 

 the lingual tonsil, and has a nodular surface covered with soft epithelium. 

 Laterally there are fold-like elevations called lenticular papillae. 



The tongue is composed of a mucous membrane (tunica mucosa) 

 and a submucous layer, together with the underlying striated muscle which 

 forms the bulk of the organ. Its anterior portion may be described first. 

 The mucous membrane is characterized by the various papillae. The 

 filiform papillae (Figs. 200 and 201) are cylindrical or conical elevations of 

 the tunica propria, each with from 5 to 20 secondary papillae at its upper 

 end. They consist of vascular fibrillar connective tissue with numerous 

 elastic fibers and are covered by a thick stratified epithelium. The outer 



epithelial cells are flat and corni- 

 fied, that is they have undergone 

 a horny hyaline degeneration, 

 and several slender columns of 

 such cells may extend beyond 

 the secondary papillae. The 

 filiform papillae are from 0.7 to 

 3.0 mm. tall. Fungiform papillae, 

 (Fig. 201) are rounded elevations 

 with a somewhat constricted 

 base. The entire outer surface 

 of their connective tissue core is 

 beset with secondary papillae. 

 They contain but little elastic tis- 

 sue; the epithelium is not as 

 thick as in the filiform papillae, 

 and its outer cells are not cornified. In life, fungiform papillae are red since 

 their epithelium transmits the color of the blood beneath. Their height 

 varies from 0.5 to 1.5 mm. The vallate papillae resemble broad fungi- 

 form papillae. They are from i to 3 mm. broad and i to 1.5 mm. tall, each 

 being surrounded by a deep groove (Fig. 202). Their connective tissue 

 often contains longitudinal, oblique, or encircling smooth muscle fibers, the 

 last named being found near the lateral walls. Secondary papillae 

 are confined to the upper wall. Occasionally the epithelium sends 

 branched prolongations into the underlying tissue. These may become 

 detached from the surface and appear as concentric bulb-like bodies such 

 as are generally known as 'epithelial pearls.' There are also branched 

 serous glands which grow down from the epithelium, having ducts 

 which open into the deep grooves (Fig. 202). The foliate papillae are 



Fat cells. Fascia linguae. Muscle. 



FIG. 200. FROM A LONGITUDINAL SECTION OP THE 

 DORSUM OP A HUMAN TONGUE. X 12. 



