Original Article

Primates

, Volume 49, Issue 3, pp 204-209

Muscle architecture of the upper limb in the orangutan

  • Motoharu OishiAffiliated withDepartment of Anatomy 1st, School of Veterinary Medicine, Azabu University Email author 
  • , Naomichi OgiharaAffiliated withLaboratory of Physical Anthropology, Graduate School of Science, Kyoto University
  • , Hideki EndoAffiliated withThe University Museum, The University of Tokyo
  • , Masao AsariAffiliated withDepartment of Anatomy 1st, School of Veterinary Medicine, Azabu University

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Abstract

We dissected the left upper limb of a female orangutan and systematically recorded muscle mass, fascicle length, and physiological cross-sectional area (PCSA), in order to quantitatively clarify the unique muscle architecture of the upper limb of the orangutan. Comparisons of the musculature of the dissected orangutan with corresponding published chimpanzee data demonstrated that in the orangutan, the elbow flexors, notably M. brachioradialis, tend to exhibit greater PCSAs. Moreover, the digital II–V flexors in the forearm, such as M. flexor digitorum superficialis and M. flexor digitorum profundus, tend to have smaller PCSA as a result of their relatively longer fascicles. Thus, in the orangutan, the elbow flexors demonstrate a higher potential for force production, whereas the forearm muscles allow a greater range of wrist joint mobility. The differences in the force-generating capacity in the upper limb muscles of the two species might reflect functional specialization of muscle architecture in the upper limb of the orangutan for living in arboreal environments.

Keywords

Pongo Upper limb Muscle architecture Locomotion