TY - JOUR
T1 - Macaque pterygoid muscles
T2 - Internal architecture, fiber length, and cross-sectional area
AU - Antón, Susan C.
N1 - Funding Information:
I am indebted to Drs. Bill Hylander, Steve Leigh, Gen Suwa, Tim White, F. Clark Howell, Sharon Swartz, and Bob Full for their help. The following individuals and institutions provided cadaveral material: Dr D. Weaver, Bowman Gray Medical Center, Wake Forest University; Yerkes Primate Research Institute; Oregon Primate Research Institute; Three Rivers Primate Research Institute, Tulane University; Kyoto Primate Research Institute. S. Schell, K. Jones, and T. C. Crawford provided technical assistance. The L. S. B. Leakey and Wenner-Gren Foundations (grant #5481 with F. C. Howell) provided funding.
PY - 2000
Y1 - 2000
N2 - Models of mastication require knowledge o f fiber lengths and physiological cross-sectional area (PCS), a proxy for muscle force. I dissected 36 medial pterygoid and 36 lateral pterygoid muscles from 30 adult females of 3 macaque species (Macaca fascicularis, M. mulatta, M. nemestrina) using gross and chemical techniques and calculated PCS. These macaques have mechanically similar dietary niches and exhibit no significant difference in muscle architecture or fiber length. Fiber length does not scale with body size (mass) for either total pterygoid muscle or for medial pterygoid muscle mass. However, fiber length scales weakly with lateral pterygoid muscle mass. In each case, differences in PCS among species result from differences in muscle mass not fiber length. Medial pterygoid PCS scales isometrically with body size; larger animals have greater force production capabilities. Medial and lateral pterygoid PCS scale positively allometrically with facial size; individuals with more prognathic faces and taller mandibular corpora have greater PCS, and hence force, values. This positive allometry counters the less efficient positioning of masticatory muscles in longer-faced macaques. PCS is only weakly correlated with bone proxies previously used to estimate muscle force. Thus, predictions of muscle force from bone parameters will entail large margins of error and should be used with caution.
AB - Models of mastication require knowledge o f fiber lengths and physiological cross-sectional area (PCS), a proxy for muscle force. I dissected 36 medial pterygoid and 36 lateral pterygoid muscles from 30 adult females of 3 macaque species (Macaca fascicularis, M. mulatta, M. nemestrina) using gross and chemical techniques and calculated PCS. These macaques have mechanically similar dietary niches and exhibit no significant difference in muscle architecture or fiber length. Fiber length does not scale with body size (mass) for either total pterygoid muscle or for medial pterygoid muscle mass. However, fiber length scales weakly with lateral pterygoid muscle mass. In each case, differences in PCS among species result from differences in muscle mass not fiber length. Medial pterygoid PCS scales isometrically with body size; larger animals have greater force production capabilities. Medial and lateral pterygoid PCS scale positively allometrically with facial size; individuals with more prognathic faces and taller mandibular corpora have greater PCS, and hence force, values. This positive allometry counters the less efficient positioning of masticatory muscles in longer-faced macaques. PCS is only weakly correlated with bone proxies previously used to estimate muscle force. Thus, predictions of muscle force from bone parameters will entail large margins of error and should be used with caution.
KW - Allometry
KW - Macaca
KW - Mandible
KW - Mastication
KW - Muscle architecture
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U2 - 10.1023/A:1005431831444
DO - 10.1023/A:1005431831444
M3 - Article
AN - SCOPUS:0034002210
SN - 0164-0291
VL - 21
SP - 131
EP - 156
JO - International Journal of Primatology
JF - International Journal of Primatology
IS - 1
ER -