Muscle architecture of the upper limb in the orangutan

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.

Standing on the shoulders of apes: Analyzing the form and function of the hominoid scapula using geometric morphometrics and finite element analysis

“…Furthermore, living specimens would probably withstand the tensile strain and stresses experienced during locomotion mostly on their shoulder soft tissues such as muscles, ligaments, and tendons rather than directly on their scapulae. Even though shoulder muscle origin and insertions for hominoids are known (Diogo et al, ,,,; Diogo and Wood, ) and physiological cross‐sectional areas of some the muscles are available for some of the analyzed species (Veeger et al, ; Keating et al, ; Thorpe et al, ; Cheng and Scott, ; Carlson, ; Oishi et al, ; Michilsens et al, ; Peterson and Rayan, ; Myatt et al, ), the specific activation patterns are unknown for the majority of the species when performing the analyzed postures. These reasons ratified the decision of carrying out simpler comparative structural analyses instead of simulating in detail loading scenarios based on unknown or uncertain information.…”

Dimensions of forelimb muscles in orangutans and chimpanzees

“…1999; Ogihara et al. 2005; Carlson, 2006) and orangutan (Payne, 2001; Oishi et al. 2008), although the muscle morphology of the hindlimb of these species has been more completely described (Thorpe et al.…”

Age-related structural changes in upper extremity muscle tissue in a nonhuman primate model

“…While the inclusion of more muscles is not expected to significantly alter the weak relationships between total PCSA and functional performance, future characterization of these architectural parameters would provide a more complete picture of age-related PCSA loss and would allow for additional comparison of the vervet muscle structure to those obtained for other non-human primates. 2,6,11,17,29,30,33 Only female vervets were included in this study. Although it is unclear if hormonal imbalances due to aging or menstrual cycle phase affect the results of this study, previous work found that lean body mass in adult human women was approximately 64% of that in men from regardless of decade of life indicating that women and men lose muscle mass at approximately the same rate.…”