| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2002: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2001: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2000: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1999: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
There are some reports about masticatory muscles of Marsupials (Davidson and Young 1990, Filan 1990, Lubosh 1908), but these reports provide little information about the innervation of these muscles. One of the most important criteria of the homology of muscles is innervation (Stark 1982, Tome et. Al 1993, 94, 98, 2002). The aim of this study was to classify the masticatory muscles of kangaroo and wombat based on their innervation. Three adult kangaroos (2 males and 1 female), four adult wombats (2 males and 2 female) fixed with 10% formalin were used for this study. The head of the specimens were cut in half in the sagittal plane. We observed the branches of the mandibular nerve, dissected the masticatory muscles, and observed the intramuscular distributions of the nerves. The temporal muscle and the masseter were classified into two parts respectively based on their innervation. The zygomaticomandibular muscle, which was located underneath the zegomatic arch, belongs to the masseter
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muscle according its innervation. The classification of masticatory muscles based on their innervation provides new insights into their structure and homology. Few studies have been carried out on the masticatory muscles in the koala (Phascolarctos cinereous). Then we focused on the masseter and temporalis complex. Three adult koalas (2 males and 2 females), fixed by injection 10% formalin solution into the carotid arteries and preserved in 50% alcohol, were dissected for this study. The dissection was carried out under a stereomicroscope. The temporalis muscle was innervated by both anterior and posterior deep temporal nerves. The masseter muscle was innervated by the masseter nerve and was divided into three layers (superficial, middle, deep) by aponeuroses. The zygomaticomandibularis muscle, which mainly originated from the medial surface of the zygomatic arch, was innervated by anterior and posterior deep temporal nerves as well as the masseter nerve. The zygomaticomandibularis muscle corresponded exactly to the intermediate muscle between the three deep layer of the masseter muscle and the temporalis muscle based on their innervation. Less
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