A text-book of dental histology and embryology, including laboratory directions . mina is continuousalong the entire extent of the ridge. The Enamel Organ.—From ten points on the surface of thelamina little buds of epiblast start and grow down into themesoderm, increasing in size and becoming bulbous at thedeep end. The bulbous portion gradually becomes this stage the bulb is composed of an outer layer of colum-nar cells, continuous with the Malpighian layer of the ridgeand a central mass of large polyhedral cells (Fig. 179).As the bud continues to grow into the mesoderm, the meso
A text-book of dental histology and embryology, including laboratory directions . mina is continuousalong the entire extent of the ridge. The Enamel Organ.—From ten points on the surface of thelamina little buds of epiblast start and grow down into themesoderm, increasing in size and becoming bulbous at thedeep end. The bulbous portion gradually becomes this stage the bulb is composed of an outer layer of colum-nar cells, continuous with the Malpighian layer of the ridgeand a central mass of large polyhedral cells (Fig. 179).As the bud continues to grow into the mesoderm, the meso-dermic tissue below it begins to condense and the cells of theupper portion of the bulb, growing more rapidly, convertthe bulb into a two-layered bag. THE DENTAL PAPILLA 363 The Dental Papillae.—The cells in the condensed mesodermmultiply and grow up into the cavity of this cap, forming thebeginning of the dental papillae. This stage is representedin Figs. 280 and 281, in which the enamel organ is seen con-nected with the lamina by a cord of epithelial cells, and Fig. 277. The dental ridge. A section through the mandible of a pig embryo at the lower edge,two spicules of bone beginning to form, to the right Meckels cartilage. made up of an outer layer of columnar cells known as theouter tunic, and an inner layer of columnar cells lying nextto the dental papillae, known as the inner tunic. The poly-hedral cells between the two layers fill the central part ofthe enamel organ and have taken on peculiar appearance,which has given to them the name of the stellate reticulum. 364 THE DEVELOPMENT OF THE TOOTH GERM The development of the tooth germ now progresses untilthe dental papilla has taken on the typical form of thetooth. The fully formed enamel organ foran incisor of asheep is shown in Fig. 282. The cord which connects theouter tunic with the surface epithelium is not shown in thissection. Fig. 278 .^gjgagll ME^Wm ;>aKShl V •• >,- •*\M59 dmmt 3 WBR?m^n .Wmt M-- J
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectteeth, bookyear1912
