家鶏下顎骨の発生学的研究
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概要
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The development of the mandible was studied in the hatching embryo, the chicken and the adult domestic fowl, and the results obtained are summarized as follows. 1. The constituent bones of the mandible include Dental, Supraangular, Splenial, Gonial and Angular. The last mentioned bone, however, lacks independence because it fuses with the Articular (at the Processus angularis internus) in the adulthood of the animal. Of the anlages of the coverning bones, those of the Supraangular and Angular appear at seven and a half days after hatching, the Dental at 8 and a half days, the Splenial at 9 days and the Angular at 10 days after hatching. Completion of the covering hones : These bones are constructed into their mature forms within 20 days after hatching, but the time needed for total completion including that of the Articular bone is 3 months after birth. If, further, the formation of the mandibular canal and the fusion of each constituent bone are therein included, the time needed for is one year after birth. 2. The formation and completion of the Articular bone : The Articular bone is formed and completed by cooperation of enchondrous and intramembranous ossifications by 3 months after birth. 3. Formation of the mandibular canal : This is made primarily by intramembranous ossification at the posterior part of the Meckel's cartilage which is then gradually fused with the Supraangular. 4. Formation of the Angular bone : The anlage of the bone develops on the 10th embryonic day at the inner side of that portion corresponding to the root of Processus angularis internus, and by the 11th day a thin layer of new bone is deposited along the process, later to increase the bulk gradually. On the 15the embryonic day cartilage cells occur on the posterior dorsal part of the bone facing the process, and on the 20th day a part of the bone is already fused with the process. By 2 months after hatching the whole constituent bones become completely integrated so that no further discrimination is feasible. 5. Fusion of the constituent bones and how it occurs : Until 6 months after birth the constituent bones are packed together dorsoventrally and in-and outwardly, but by the 12 th month after birth they are almost fused. The fusion takes place as metaplasmatic bone formation especially with regard to the Gonial, Supraangular and the posterior part of the Angular fitting into the concavity on the ventral side of the Articular. 6. Later course of the Meckel's cartilage : After the formation of the Articular bone, the remaining cartilage gradually shorten its antero-posterior length by intramembranous ossification arising from its front and rear peripheries.
- 九州歯科学会の論文
- 1957-12-31