Branching patterns of the vascularization and innervation of the primate forelimb

Abstract

In this study, we investigate the branching patterns of the vascularization and innervation of the primate forelimb by performing detailed dissections of five unembalmed nonhuman primate specimens belonging to five different species, that is, rhesus macaque (Macaca mulatta), white-handed gibbon (Hylobates lar), Western gorilla (Gorilla gorilla), chimpanzee (Pan troglodytes), and bonobo (Pan paniscus). Results are compared with five embalmed human specimens (Homo sapiens), and anatomical data of previous studies on nonhuman primates are also included to provide a broader comparative framework. The results show that the overall configuration of the forelimb blood vessels and nerves of the different primate species is similar, although some apparent interspecific differences are found. In all nonhuman primates, in contrast to humans, the superficial vena basilica is absent. Moreover, in gorilla, chimpanzee, and bonobo, the superficial vena cephalica is confined to the forearm. In humans, both an arteria interossea anterior and posterior are present, while in nonhuman primates, only an arteria interossea anterior is present, which migrates to the posterior side at the level of the musculus pronator quadratus. For the innervation, the nervus (n.) medianus and n. ulnaris connect in the forearm of the gorilla and macaque. In the gibbon, the brachial plexus shows some differences in the branching pattern at the fasciculus level compared to the other primates. We conclude that the forelimb innervation branching pattern shows some minor differences between the nonhuman primate species, compared to higher plasticity in the vascularization. However, the exact functional implications of these differences still remain unclear. Therefore, more research on a broader range of primate species and sampling more specimens for each taxon are needed.

Keywords: apes; arm; blood vessels; monkeys; nerves.