Tomo S, Tomo I, Townsend G C
Department of Anatomy, School of Medicine, St. Marianna University, Kawasaki, Japan.
Anat Rec. 1998 Jul;251(3):346-50. doi: 10.1002/(SICI)1097-0185(199807)251:3<346::AID-AR10>3.0.CO;2-O.
Although the human digastric muscle is classified as a suprahyoid muscle, none of the digastric muscles in other mammals are classed as suprahyoid in textbooks of veterinary anatomy. The aim of this study was to describe the anatomical relationship of the digastric muscle in a marsupial, the kangaroo, and to consider factors thought to be important in leading to the different position of the muscle in quadrupeds compared with humans. Eight heads of the common wallaroo (Macropus robustus) were used in this study. They were fixed by injection of 10% formalin solution into the carotid arteries and dissected under a stereomicroscope. The digastric muscle in the common wallaroo arose from the paroccipital process of the temporal bone and inserted into the mandible but had no intermediate tendon or any connection with the hyoid bone. It was supplied by both the mandibular and facial nerves. The hyoglossus muscle attached to the inferior surface of the hyoid bone and its ventral border overlapped the mylohyoid muscle. The hypoglossal nerve passed between these two muscles. Therefore, in contrast to humans, the digastric, hyoglossus, and mylohyoid muscles in the kangaroo were all located inferior to the hyoid bone. Differences in head posture and the position of the larynx between kangaroos and humans may account for the observed difference in the digastric muscle's position relative to the hyoid bone between these species.
尽管人类的二腹肌被归类为舌骨上肌，但在兽医解剖学教科书中，其他哺乳动物的二腹肌均未被归类为舌骨上肌。本研究的目的是描述有袋动物袋鼠的二腹肌的解剖关系，并探讨与人类相比，导致该肌肉在四足动物中位置不同的重要因素。本研究使用了8个普通大袋鼠（Macropus robustus）的头部。通过向颈动脉注射10%福尔马林溶液进行固定，并在体视显微镜下进行解剖。普通大袋鼠的二腹肌起自颞骨的枕突，止于下颌骨，但没有中间腱，也与舌骨没有任何连接。它由下颌神经和面神经共同支配。舌骨舌肌附着于舌骨的下表面，其腹侧缘与下颌舌骨肌重叠。舌下神经在这两块肌肉之间穿过。因此，与人类不同，袋鼠的二腹肌、舌骨舌肌和下颌舌骨肌均位于舌骨下方。袋鼠和人类头部姿势及喉部位置的差异可能是导致这两个物种中二腹肌相对于舌骨位置差异的原因。
