TONGUE 



231 



Primary 

 papilla. 



Secondary 

 papillae. 



Filiform process. 



toward the throat, is the foramen oecum. On either side of the tongue, 

 as indicated in the figure, there are from three to eight parallel vertical 

 folds (2-5 mm. long) occurring close together; these are the foliate 

 papillcs. In the foliate and vallate papillae the organs of taste are most 

 numerous. The under surface of the tongue is free from epithelial 

 papillae; its mucosa resembles that which lines the mouth. The posterior 

 part of the tongue has a nodular surface covered with soft epithelium 

 and contains the lingual tonsil, which has already been described. Later- 

 ally it presents fold-h'ke elevations called lenticular papillce. 



Filiform papillae (Fig. 221) are slender cornified epithelial projections, 

 composed of pointed cells which are described as stacked like super- 

 imposed hollow cones. The cells 

 have undergone a horny hyaline 

 degeneration. These projec- 

 tions are arranged in clumps 

 which rest upon a group of from 

 five to twenty connective tissue 

 elevations, or secondary papillae ; 

 and these in turn are at the 

 summit of a cylindrical or coni- 

 cal primary papilla, composed 

 of vascular connective tissue 

 with numerous elastic fibers. 

 These primary papillae form the 

 basal portions of the filiform 

 papillae. They are well shown 

 in Fig. 222, along with the secondary papillae, but the cornified processes 

 of the thick epithelium above them have undergone post-mortem disin- 

 tegration. Most of the papillae of the tongue are of the filiform type. 



Fungiform papillae (Fig. 222) are rounded elevations with a somewhat 

 constricted base, varying in height from 0.5 to 1.5 mm. In life they are 

 red, since their epithelium is not cornified and transmits the color of the 

 blood beneath. They contain a primary connective tissue papilla, with 

 but few elastic fibers, beset on all sides with secondary papillae. 



The vallate papillae resemble broad fungiform papillae. They are 

 from i to 3 mm. broad and i to 1.5 mm. tall, each being surrounded by a 

 deep groove (Fig. 223). Their connective tissue often contains longi- 

 tudinal, 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 



. Fat cells. 

 FIG. 221. FROM 



Fascia linguae. 



Muscle. 



LONGITUDINAL SECTION OF THK 



DORSUM OF A HUMAN TONGUE. X 12. 



