MOUTH CAVITY. 



165 



Papillae filiformes ; 

 Papillae fungiformes ; 

 Papillae circumvallatae. 



ThQpapillcefiliform.es (Fig. 120) are 0.7-3 mm. in length, 

 round or pointed, and covered by a layer of cornified flat 

 stratified epithelium. This in some animals (e. g., cats) forms 

 a sharp, pointed projection of hard epithelial cells. The tunica 

 propria under the epithelium shows several (five to twenty) 

 small papillae, the secondary papillce, which correspond with 

 the vascular papillae of the skin. The filiform papillae are 

 distributed over the entire upper surface of the tongue. 



The papillce fungiformes (Fig. 121) are 0.7-1.8 mm. in 

 length, and have a round form which suggests that of a small 



FIG. 121. 



'i^N 



Secondary 

 papilla 





Perpendicular section through a papilla fungiforniis of the human tongue. X 45. 



mushroom. They are present mainly on the anterior part of 

 the tongue, and are distinguished easily from the other papilla 

 by their red color, which is due to their thin epithelial covering 

 and rich blood supply. They are covered with epithelium 

 similar to that of the mouth cavity, and show many secondary 

 papillae. 



