. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 176 OSSIFICATION OF THE CHONDROCRANIUM separated at an early stage before the ossification has made much progress. Absorption of the body of the sphenoid bone to form the sphenoidal cells, of the frontal to form the frontal sinuses, and of the maxillaries to form the maxillary antra is also produced by outgrowths of the nasal mucous membrane, all these cavities, as well as the ethmoidal cells, being continuous with the nasal cavities and lined with an epithelium which is continuous with the m
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. 176 OSSIFICATION OF THE CHONDROCRANIUM separated at an early stage before the ossification has made much progress. Absorption of the body of the sphenoid bone to form the sphenoidal cells, of the frontal to form the frontal sinuses, and of the maxillaries to form the maxillary antra is also produced by outgrowths of the nasal mucous membrane, all these cavities, as well as the ethmoidal cells, being continuous with the nasal cavities and lined with an epithelium which is continuous with the mucous membrane of the nose. In the lower mammalia the erosion of the mesial surface of the ectethmoidal cartilages results, as a rule, in the formation of five conchae, while in man but three are usually recognized. Not infrequently, however, the human middle concha shows indications, more or less marked, of a division into an upper and a lower portion, which corre- spond to the third and fourth bones of the typical mammalian arrange- ment. Furthermore, at the upper portion of the nasal wall, in front of the superior concha, a slight elevation, termed the agger nasi, is always observa- ble, its lower edge being prolonged down- ward to form what is termed the uncinate process of the ethmoid. This process and the agger together represent the up- permost concha of the typical arrange- ment, to which, therefore, the human arrangement may be reduced. A number of centers of ossifica- tion—the exact number is yet uncer- tain—appear in the periotic capsule during the later portions of the fifth month, and during the sixth month these unite together to form a single center from which the complete ossi- fication of the cartilage proceeds to form the petrous and mastoid portions of the temporal bone (Fig. 109, p). The mastoid process does not really form until several years after birth, being produced by the hollowing and bulging out of a portion of the petrous bone by out-growths fro
Size: 1588px × 1573px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookautho, bookcentury1900, bookdecade1910, booksubjectembryology
