614 



THE DIGESTIVE SYSTEM 



(4) Finally, the dental-sac tissue between these two bony surfaces forms 

 the peridental membrane, a thin, fibrous, connective-tissue layer whose 

 fibers are attached to the cementum and to the spongy bone of the 

 socket. In other words, the cemental bone of the root and the spongy 

 bone of the socket become sutured together by means of the inter- 

 locking fibers of the peridental membrane. This type of suture, which 







TONGUE ^'♦f -''-• ;°*'i*« •^.* •.•," "NJ Z'^^r'/''^''''-'"''''^ 



MESENCHYME 



TOOTH GER 

 MILK TOOT 

 MANDIBLE 

 BONE FORMATION 

 MECKEL'S OUTER ENAMEL 



CARTILAGE LATER 



ENAMEL PULP '^ 



INNER ENAME 



Fig. 288. Tooth development in the pig. (A) Upper and lower jaw region of 18 mm. 

 pig embryo showing labial and gum areas with the labia! groove insinuated between. (B) 

 Section through snout and upper and lower jaws of 30-mm. pig embryo showing formation 

 of nasal passageways, secondary palate, lip, gum, and jaw regions, and ingrowing dental 

 ledge. (C) High-powered drawing of dental ledge shown in square C in figure B. (D) 

 Section similar to B in 65-mm. pig embryo. (E) Enlargement of area marked E in D 

 showing dental papilla and enamel organ. (F) Drawing showing juxtaposition of inner 

 layer of enamel organ (the anjeloblast layer) and the odontoblast cells which differentiate 

 from the mesenchyme of the dental papilla. 



