アカゲザル若年期の下顎骨についての形態学的研究
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概要
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Fifty mandibles of Rhesus monkeys, a member of macaque of primates, were morphologically studied. These mandibles were of the youth with M_3 unerupted. These mandibles were classified in accordance with the degree of teeth eruption, and developmental state of the mandibles was examined. The results were as follows : 1. Development of the attachment point to the mandible of the masticatory muscles were slight because of young age. However the pterygoid rough was comparatively well developed. 2. The mental foramen averaged 0.91mm in diameter and its size was not related to the eruption of teeth. The mental foramen was located directly under m_1 in the deciduous dentition group, below and between m_1 and m_2 in the mixed dentition group with first molars erupted, and below p_2 in the permanent dentition group with second molars erupted. The height of the position of the mental foramen was slightly below the center. This is slightly lower than humans. The opening of the mental foramen was directed anterosuperiorly or anteriorly in many of the deciduous dentition group, and anteroinferiorly in many cases with the eruption of molars. 3. The mandibular foramen averaged 1.85mm in diameter, but gradually enlarged with eruption of teeth. The diameter was 2.26mm with the eruption of M_2. The height of the mandibular foramen was slightly lower than the center for the deciduous dentition group, moved upward with eruption of teeth, and was located about the center with the eruption of M_2. 4. The form of the mandibular head is elliptic and elongated in the right and left directions. In carnivore, the form is much more elongated and pigs and wild boars present a nearly square form with the width and thickness of the mandibular head about the same. 5. The mandibular notch showed an index of 36.71. The depth of the notch is shallower than humans but deeper than dogs. As compared with pigs and wild boars, the depth is shallower. The notch gets shallower along with eruption of teeth. 6. Each measurement for the mandibles increses in magnitude with eruption of teeth. However, the mandibular angle does not change at all. The rates of increase for the mandibular length and height are high as compared with the width. 7. Thomson's mandibular index is 91.41, which indicates that the inter-mandibular heads width is slightly greater than the mandibular length. With eruption of teeth, the indexes get larger and indicate that the rate of increase for the mandibular length is significantly larger than that for the width. 8. The height of the coronoid process is slightly higher than that of the condylar process. In carnivore such as dogs, the height of the coronoid process is twice that of the condylar process. Differences were seen between various animals.
- 1984-04-25