162 



THE DIGESTIVE SYSTEM 



In the papillary region four types of papillte may be found, 

 namely, filiform, fungiform, foliate, and circumvallate. 



Filiform papilla? are the most numerous and oceiu" in rows through- 

 out the papillary zone. Each is formed by a conical core of con- 

 nective tissue that projects well out beyond the general surface of 



Fig. 100. — Diagram of three different types of tongue papillae. 

 filiform; Fu., fungiform. 



v., vallate; Fi. 



the tongue and is covered by the stratified squamous epithelium. 

 The superficial cells of the epithelium of these papillae in some 

 animals become heavily cornified and present a rough, file-like 

 surface that is useful in masticating food. 



Fig. 101. — Section through foliate papillae of rabbit, showing von Ehoner's glands in 

 the underlying tissues. 



Fungiform pa])illa> are much fewer in number than the filiform 

 and are scattered irregularly over the papillary region among the 

 filiform papillae. They are formed by extensions of the connective 

 tissue that broaden out as they rise above the general \eye\ of the 

 tongue. The e])ithelial covering is thin, so that these paiiilhe ai)pear 



