THE ORAL CAVITY 



163 



red, (kie to the hlood of the uii(I(m-|\ iiii;- coiincctixt' tissue sl)()\viii<j; 

 throii^di. Taste-l)U(ls may ai)i)ear in the side waHs of the fuii^nform 

 pa])ilhe. 



FoHate papilhe (Fij^;. 101), as the iiaiiie iinphes, are leaf-hke and 

 occur along each hiteral margin of tlie tongue toward the reai- of 

 the i)a])inary zone. Tliey occur in varying nund)ers as narrow, 

 parallel, consecutive, vertical ridges separated by furrows. They 

 are poorly defined in man but well rei)resented in such animals as 

 the rabbit and opossum. Here they may be seen as an oblong ])atch 

 on each side of the tongue. The primary pa])illa of comiective 

 tissue has three definite secondary ])r()jections oxer which the 

 epithelial coat forms a smooth sur- 

 face. Numerous taste-buds occur 

 in the lateral epithelial walls of 

 these papilhie. (Fig. 102.) 



The circumvallate or vallate 

 papillte occur just in front of the 

 foramen cecum, which is a shallow 

 depression posterior to the papil- 

 lary region. They are arranged in 

 a V-shaped pattern, with the apex 

 of the "V" toward the foramen 

 cecum, are few in number, and are 

 the largest type of papillae. Each 

 has a knob-shaped form with a flat 

 top and is surrounded by a deep 

 furrow or fossa, so that the papilla 

 does not project above the general 

 level of the tongue. The primary 

 connective-tissue papilla is divided into a number of smaller sec- 

 ondary papillae covered with stratified squamous epithelium. 

 Numerous taste-buds occur in the epithelium of the side walls 

 and in the epithelium of the opposite wall of the fossa. 



The blood vessels and nerves for all types of i)apillae are sup- 

 ported in the connective-tissue core. Fibers of the gustatory nerve 

 pass to the sensory cells of the taste-buds located in the \'arious 

 papilla^. Each taste-bud is somewhat cask-shaped; the epithelial 

 wall is formed by fiat fusiform epithelial cells that are arranged like 

 the staves of a cask. One end of this cask-like bud is open and faces 

 the fossa (furrow) about the papilla. The space within the wall 

 of fiat epithelial cells is occupied by two kinds of specialized epithe- 



FiG. 102. — Photograph of taste- 

 buds in the walls of the foliate papillte 

 of the rabbit. 



