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EMG of the digastric muscle in gibbon and orangutan: functional consequences of the loss of the anterior digastric in orangutans.

Publication ,  Journal Article
Wall, CE; Larson, SG; Stern, JT
Published in: American journal of physical anthropology
August 1994

Unlike all other primates, the digastric muscle of the orangutan lacks an anterior belly; the posterior belly, while present, inserts directly onto the mandible. To understand the functional consequences of this morphologic novelty, the EMG activity patterns of the digastric muscle and other potential mandibular depressors were studied in a gibbon and an orangutan. The results suggest a significant degree of functional differentiation between the two digastric bellies. In the gibbon, the recruitment pattern of the posterior digastric during mastication is typically biphasic. It is an important mandibular depressor, active in this role during mastication and wide opening. It also acts with the anterior suprahyoid muscles to move the hyoid prior to jaw opening during mastication. The recruitment patterns of the anterior digastric suggest that it is functionally allied to the geniohyoid and mylohyoid. For example, although it transmits the force of the posterior digastric during mandibular depression, it functions independent of the posterior digastric during swallowing. Of the muscles studied, the posterior digastric was the only muscle to exhibit major differences in recruitment pattern between the two species. The posterior digastric retains its function as a mandibular depressor in orangutans, but is never recruited biphasically, and is not active prior to opening. The unique anatomy of the digastric muscle in orangutans results in decoupling of the mechanisms for hyoid movement and mandibular depression, and during unilateral activity it potentially contributes to substantial transverse movements of the mandible. Hypotheses to explain the loss of the anterior digastric should incorporate these functional conclusions.

Duke Scholars

Published In

American journal of physical anthropology

DOI

EISSN

1096-8644

ISSN

0002-9483

Publication Date

August 1994

Volume

94

Issue

4

Start / End Page

549 / 567

Related Subject Headings

  • Tongue
  • Tendons
  • Pterygoid Muscles
  • Pongo pygmaeus
  • Neck Muscles
  • Muscle Contraction
  • Movement
  • Mastication
  • Masseter Muscle
  • Mandible
 

Citation

APA
Chicago
ICMJE
MLA
NLM
Wall, C. E., Larson, S. G., & Stern, J. T. (1994). EMG of the digastric muscle in gibbon and orangutan: functional consequences of the loss of the anterior digastric in orangutans. American Journal of Physical Anthropology, 94(4), 549–567. https://doi.org/10.1002/ajpa.1330940408
Wall, C. E., S. G. Larson, and J. T. Stern. “EMG of the digastric muscle in gibbon and orangutan: functional consequences of the loss of the anterior digastric in orangutans.American Journal of Physical Anthropology 94, no. 4 (August 1994): 549–67. https://doi.org/10.1002/ajpa.1330940408.
Wall CE, Larson SG, Stern JT. EMG of the digastric muscle in gibbon and orangutan: functional consequences of the loss of the anterior digastric in orangutans. American journal of physical anthropology. 1994 Aug;94(4):549–67.
Wall, C. E., et al. “EMG of the digastric muscle in gibbon and orangutan: functional consequences of the loss of the anterior digastric in orangutans.American Journal of Physical Anthropology, vol. 94, no. 4, Aug. 1994, pp. 549–67. Epmc, doi:10.1002/ajpa.1330940408.
Wall CE, Larson SG, Stern JT. EMG of the digastric muscle in gibbon and orangutan: functional consequences of the loss of the anterior digastric in orangutans. American journal of physical anthropology. 1994 Aug;94(4):549–567.
Journal cover image

Published In

American journal of physical anthropology

DOI

EISSN

1096-8644

ISSN

0002-9483

Publication Date

August 1994

Volume

94

Issue

4

Start / End Page

549 / 567

Related Subject Headings

  • Tongue
  • Tendons
  • Pterygoid Muscles
  • Pongo pygmaeus
  • Neck Muscles
  • Muscle Contraction
  • Movement
  • Mastication
  • Masseter Muscle
  • Mandible