Satoh K
Department of Zoology, Faculty of Science, Kyoto University, Japan.
J Morphol. 1999 Apr;240(1):1-14. doi: 10.1002/(SICI)1097-4687(199904)240:1<1::AID-JMOR1>3.0.CO;2-D.
The actions of masticatory muscles in relation to transverse grinding, associated with forward masticatory movement of the mandible, were investigated by using a mechanical model in the two murid rodents, the Japanese field mouse (Apodemus speciosus: subfamily Murinae) and the gray red-backed vole (Clethrionomys rufocanus: subfamily Arvicolinae). Furthermore, statics of the masticatory system on a sagittal plane while chewing is taking place were also analyzed in these rodents. The inward grinding movements of hemimandibles are generated by the posterior temporalis and internal and external pterygoids in both species. In addition to these muscles, the anterior temporalis also moves the hemimandibles lingually in Apodemus speciosus. The area of origin of the external pterygoid seems more advantageous for transverse grinding in A. speciosus than in Clethrionomys rufocanus. On the basis of the static analysis, the anterodorsal area of origin of the external pterygoid to the upper second and third molars in Clethrionomys rufocanus appears to be an adaptive character to prevent the jaw joints from dislocation during occlusion at a posterior point on the elongated row of cheek teeth.
通过使用机械模型，对两种鼠科啮齿动物——日本田鼠（姬鼠属：鼠亚科）和灰背红腹田鼠（棕背田鼠属：田鼠亚科）下颌骨向前咀嚼运动相关的咀嚼肌在横向研磨时的作用进行了研究。此外，还对这些啮齿动物在咀嚼时矢状面上咀嚼系统的静力学进行了分析。在这两个物种中，半侧下颌骨的向内研磨运动是由颞肌后部以及翼内肌和翼外肌产生的。除了这些肌肉外，在日本田鼠中，颞肌前部也会使半侧下颌骨向舌侧移动。翼外肌的起始区域在日本田鼠中似乎比在灰背红腹田鼠中更有利于横向研磨。基于静态分析，灰背红腹田鼠中翼外肌到上第二和第三磨牙的前背侧起始区域似乎是一种适应性特征，可防止在伸长的颊齿列后端咬合时下颌关节脱位。
