The Inner (Alimentary) Tube and Its Respiratory Derivativi 



growth lines 



in enamel 



oral epithelium 



pulp chamber 



growth lines 



in dentine 



bone of 

 mandible 



blood vessels 

 and nerves to 



Fig. 31. Schematic diagram showing the topography of a tooth and its relations 

 to the hone of the jaw. The numbered zones indicate empirically the sequence of 

 deposition of the dentine and enamel. The so-called growth lines in the dentine and 

 enamel follow the general contours indicated by the dotted lines in the figure but 

 are much more numerous. (Courtesy, Patten: "Embryology of the Pig," Phila- 

 delphia, The Blakiston Company.) 



Cement, resembling bone, covers the root of the tooth as a rela- 

 tively thin layer. Like bone, the cement contains cells lodged in 

 lacunas (Fig. 33) connected with one another by canaliculi. The min- 

 eral constituents are like those of bone. Surrounding the root is a con- 

 nective-tissue dental sac or membrane continuous with the investing 

 membrane (periosteum) of the surface of the bony alveolus and, at 

 the neck, continuous with the mesodermal layer underlying the oral 

 epithelium covering the "gum" (gingiva). 



The central pulp-cavity is filled mainly with connective tissue con- 

 taining blood-capillaries and nerves which enter the tooth through a 



