Craniofacial Muscles

Chapter 6
Masticatory Muscle Structure and Function
Mark Lewis , Nigel Hunt, and Rishma Shah
6.1 Introduction
The muscle group referred to as the muscles of mastication includes the temporalis,
the medial and lateral pterygoid, and the masseter muscles on both sides of the face
and jaws. These voluntary skeletal muscles are derived from the paraxial mesoderm
of the fi rst branchial arch whilst their connective tissue components are derived
from mesenchymal cells of neural crest origin. They are innervated by the mandibular
division of the fi fth (trigeminal) cranial nerve (CNV). Precision in the control of
jaw position and movement of the mandible is provided by the human mandibular
locomotor system. It is important to remember that this control of both jaw position
and function varies considerably throughout the life of an individual, principally to
support the activities of providing nutrition, speaking, and swallowing. For example,
in the newborn infant very fi ne movements of the jaw are associated with the important
tongue activity necessary for breast or bottle-feeding. Subsequently, as the
deciduous teeth erupt and later as the permanent teeth erupt, these changes in dentition
are associated with periods of rapid growth of the individual in general, and
therefore the need to create increased biting and chewing forces is developed. There
may be altered demands in relation to the ravages of such conditions as dental caries
and periodontal disease with the possibility that teeth may need to be extracted or
M. Lewis , Ph.D. (*)
School of Sport, Exercise and Health , Loughborough University, Loughborough,
Leicestershire, UK and UCL Eastman Dental Institute, London, UK
e-mail: mlewis@eastman.ucl.ac.uk
N. Hunt , Ph.D., MOrth., R.C.S. • R. Shah , Ph.D., MOrth., R.C.S.
UCL Eastman Dental Institute , 256 Grays Inn Road , London WC1X8LD , UK
L.K. McLoon and F.H. Andrade (eds.), Craniofacial Muscles: A New Framework
for Understanding the Effector Side of Craniofacial Muscle Control,
DOI 10.1007/978-1-4614-4466-4_6, © Springer Science+Business Media New York 2013
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