TONGUE. 



177 



FIG. 198. FLOOR OF THE PHARYNX OF A 10 MM. 



HUMAN EMBRYO. 



I-IV. Bronchial arches; t 1 , anterior part of the tongue; t 2 , 

 second arch, joining the posterior part of the tongue 

 toward the median line. The thyreoid gland is dotted. 

 The epiglottis extends over the 4th arch. (From 

 McMurrich, after His.) 



as shown in Fig. 198. In this figure the upper jaw and roof of the pharynx 

 have been cut away; the branchial clefts are seen as dark depressions 

 bounded laterally by thin 

 plates. The first branchial 

 arch (i) is between the oral 

 and auditory clefts. In the 

 median ventral line an eleva- 

 tion (tuberculum impar) arises 

 between this arch and the 

 second; it becomes contin- 

 uous with a larger elevated 

 portion of the mandibular arch 

 to form the anterior part of 

 the tongue (t 1 ). The second 

 and third arches unite toward 

 the median ventral line and 

 there produce the posterior 

 part of the tongue (t 2 ). Be- 

 tween the anterior and poste- 

 rior parts is the opening of the thyreoglossal duct, later the foramen 

 caecum. The epiglottis is an elevated part of the third arch separated 



from the posterior part of the tongue by a 

 curved groove. 



In the adult, Fig. 199, the dorsum of the 

 anterior part of the tongue is covered with 

 papillae. These are chiefly the slender fili- 

 form papillae and conical papillae, but knob- 

 like forms, the fungiform papillae, are scat- 

 tered among them over the entire surface. 

 Near the junction of the anterior and pos- 

 terior parts of the tongue there is a V-shaped 

 row of larger papillae, generally 6 to 12 in 

 number, called vallate papillae. Their name 

 refers to the deep narrow depression which 

 encircles them. Behind the apex of the V, 

 which is directed toward the throat, is the 

 foramen caecum. On either side of the tongue, 

 as indicated in the figure, there are from 3 

 to 8 parallel vertical folds (2-5 mm. long) 



occurring close together; these are the foliate papillae. In the foliate and 

 vallate papillae the organs of taste are most numerous. The under sur- 



FIG. 199. THE UPPER SURFACE OF 

 THE ADULT TONGUE. 



c., Conical papillae; ep., epiglottis; 

 f., foliate papillae; f. c., foramen 

 caecum ; f .f ., position of the fili- 

 form and fungiform papillae ; 1., 

 lenticular papillae; 1. t., lingual 

 tonsil; p. t., palatine tonsil; v., 

 vallate papillae. 



