258 



ANATOMY FOR NURSES 



[Chap. XIV 



jaw-bones (the alveolar processes) contain sockets for the recep- 

 tion of the teeth. A dense insensitive fibrous membrane covered 

 by smooth mucous membrane — the gums — covers these pro- 

 cesses and extends a little way into each socket. These sockets 

 are lined by periosteum, which connects with the gums and serves 



POLP-CAVITY \ 



Fig. 149. — Section cf Hu.\ian Molar Tooth. Magnified. (Dalton.) 



(1) to attach the teeth to their sockets, and (2) as a source of nour- 

 ishment. 



Each tooth consists of three portions: (1) the root, consisting 

 of one or more fangs contained in the socket ; (2) the crotvn, 

 which projects beyond the level of the gums; and (3) the neck 

 or constricted portion between the root and the crown, which is 

 enveloped by the gum. 



Each tooth is composed principally of dentine, which gives it 

 shape and encloses a cavity, the pulp cavity. The dentine of the 

 crown is capped with a dense layer of enamel. The dentine of the 

 root is covered by cement. These three substances, enamel, 

 dentine, and cement, are all harder than bone, enamel being 

 the hardest substance found in the body. They are developed 

 from epithelial tissue. The pulp cavity is just under the crown and 



