. Quain's elements of anatomy . um of the enamel-germ whichhad escaped obliteration. Similar bodies are found in other situations whereepithelium is included in a seam, and is undergoing obliteration, as along the lineof closm-e of the palate (Epstein). Development of the permanent Teeth.—^Ten permanent teeth in each jawsucceed the milk-teeth, and six are superadded further back in the jaw. It willbe convenient to treat fiist of the ten anterior teeth or teeth of succession. The sacs and pulps of these teeth have their foundations laid before birthbehind those of the milk set. It will be remem
. Quain's elements of anatomy . um of the enamel-germ whichhad escaped obliteration. Similar bodies are found in other situations whereepithelium is included in a seam, and is undergoing obliteration, as along the lineof closm-e of the palate (Epstein). Development of the permanent Teeth.—^Ten permanent teeth in each jawsucceed the milk-teeth, and six are superadded further back in the jaw. It willbe convenient to treat fiist of the ten anterior teeth or teeth of succession. The sacs and pulps of these teeth have their foundations laid before birthbehind those of the milk set. It will be remembered that behind each milk-foUicle there is formed about the sixteenth week a small epithelial growth (, B,//) ; fig. 486, 4), derivedfrom the neck of the enamel-germ, and this formsthe enamel-germ of the corresponding permanent tooth. They are ten in numberin each jaw, and are formed successively from before backwards. These germssoon elongate and recede into the substance of the gum behind the germs of the Fig. Fig. 487.—Sketches showixg the eelations of the temporart and permanentDENTAL SACS AND TEETH (after Blake, With some additions). The lower parts of the first three figures, which are somewhat enlarged, representsections of the lower jaw through the alveolus of a temporary incisor tooth : a, indicatesthe sac of the permanent tooth ; c, its pedicle ; b, the sac of the milk tooth or the milktooth itself; a, V, indicate the bony recesses in which the permanent and temporaryteeth are lodged, and c, the canal by which that of the former leads to the surface of thebone behind the alveolus of the temporary tooth. The fourth and fifth figures, which arenearly of the natural size, show the same relations in a more advanced stage, in IV.,previous to the change of teeth, in V., when the milk tooth has fallen out and the per-^manent tooth begins to rise in the jaw; c, the orifice of the bony canal leading to theplace of the j)ermanent tooth. milk teeth. In the mea
Size: 2295px × 1089px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., boo, bookcentury1800, booksubjectanatomy, booksubjecthumananatomy
