1118 



DIGESTIVE SYSTEM 



Structure. — As sho\\Ti in longitudinal section (fig. 873), each tooth has a central cavity 

 [cavum dentis] or pulp cavity, which is filled with pulp [pulpa dentis]. The pulp is a soft fibrous 

 tissue richly supplied with vessels and sensory nerves which enter the root canal through the 

 apical/oramen [foramen apicis dentis]. The body of the tooth, both cro\\Ti and root, is composed 

 of a dense modified variety of bone called dentine [substantia eburnea]. It is yellowish in 

 colour. The striated appearance of the dentine is due to numerous fine canals, the dentinal 



—■ Fig. 868. — Teeth of an Adult, External View. 



Incisors Canine Premolar Molars Wisdom tooth 



Upper or 

 maxillary 

 teeth 



Fig. 869. — Teeth of Adult, Lingual Fig. 870. — Teeth of Adult, Labial and 

 Surfaces. (Broomell and Fischelis.) Buccal Surfaces. (Broomell and Fische- 



lis.) 



Fig. 871. — Canine Tooth, Lingual Surface. Fig. 872. — A Molar Tooth in Section. 



Root 



Cusp — (7^^^!^^ 



-Pulp cavity 



— Neck 



— Cingulutn 



Crown 



tubules. These contain 'Tomes' fibrils,' which are long protoplasmic branches of the odonto- 

 blasts, a layer of cells on the surface of the pulp. At the outer surface of the dentine are numer- 

 OU.S small, irregular in<cT(/^>/;«/ar s/^aces, corresi)()ndiiig in the root to Tomes' 'granular sheath' 

 (fig. 873j. The (hsntinc of tlio crown is covered with a layer of white enamel [substantia 

 adamantina], which is the hardest substance in the body. It is composed of numerous minute 



Root 



