Lamination of the Masticatory Muscles in the Phascolarctos cinereus(Koala) According to Their Innervations
Koh NAKAJIMA1 and Grant TOWNSEND2
1Department of Oral Anatomy and Developmental Biology, Showa University, School of Dentistry Hatanodai 1-5-8, Shinagawa-ku, Tokyo, Japan, 142-8555
2Dental School, The University of Adelaide, Adelaide, South Australia, Australia 5005
The masticatory muscles are usually classifed into four groups: masseter, temporalis, lateral pterygoid and medial pterygoid. The communicating muscle bundle between the temporalis and masseter called the zygomaticomandibular muscle exists. The laminations within these muscles are commonly separated by aponeuroses. Nerves control the action of muscles, so improved understanding about innervation patterns in the masticatory muscles is important in the consideration of muscle function. In this study, we focus on the relationships between the nerves supply and the lamination of masticatory muscles in Phascolarctos cinereus (Koala). The masseter muscle consists of superfcial and deep muscle layers. The superfcial muscle layer of the masseter muscle is divided into rostro-lateral and caudo-internal nerve layers. The deep muscle layer of the masseter muscle is divided into rostral, rostro-lateral, medial and caudo-internal nerve layers. The nerves that innervate the zygomaticomandibular muscle are distributed to the lateral area of the coronoid process. The temporalis muscle was divided into internal layer of the coronoid process, a lateral layer of the coronoid process and a posterior layer by the nerve distribution pattern. The medial pterygoid muscle divided into rostro-internal, medial and caudo-lateral nerve layers.