266 ANATOMY AND PHYSIOLOGY FOR NURSES 



or hypoglossal nerve, is the motor nerve of the tongue. 

 It also helps to bring the tongue, fauces, esophagus, and 

 larynx together, which is necessary in order to get the full 

 effect of taste. 



The mucous membrane covering the under surface of 

 the tongue is exactly like that lining the remainder of the 

 oral cavity. The mucous membrane upon the dorsum of 

 the tongue, instead of being thin and smooth, is thick and 

 rough due to the presence of papilla. These structures 

 are papillary projections of the corium and are of three 

 varieties. The largest or circumvaUate papilla, from eight 

 to ten in number, form an inverted V at the back of the 

 tongue (Fig. 140). The fungiform papilla are found 

 chiefly at the tip and side of the tongue. The filiform 

 papilla are distributed over the anterior two-thirds of the 

 dorsum. 



THE ORGANS OF SMELL 



The sense of smell is located in the mucous membrane 

 of the nose. To understand fully the sense of smell, a 

 knowledge of the structure of the nasal cavity and the 

 distribution of the olfactory nerve is necessary. 



The nose is composed of bones, fibrocartilages, mucous 

 membrane, and an outer covering of integument. The 

 bones that make up the nose are the nasal and the nasal 

 processes of the upper jaw (superior maxillary). The 

 fibrocartilages are five in number, and give form and stabil- 

 ity by their elasticity to the framework of the nose, at 

 the same time guarding against injury. The mucous 

 membrane, which lines the interior of the nose, is continuous 

 with the skin externally and with the lining membrane 

 of the nasal fossae. The margins of the nostrils are pro- 

 vided with numerous hairs that serve to protect the deli- 

 cate membrane of the nose against the entrance of irri- 

 tating substances. 



