The Nerve Bundle via the Median Nerve Innervating the Ulnar Intrinsic Muscles of the Hand in a Gorilla Equivalent to the Deep Branch of the Ulnar Nerve in the Human

抄録

The ulnar antebrachial branch of the median nerve (UABM) was found in the right forelimb of a female western gorilla (Gorilla Gorilla) estimated 40 years old. It branched off the median nerve at the anterior aspect of the elbow and ran ulno-distally in the forearm toward the wrist. In the distal forearm, it bifurcates into the ulnar and radial bundles; the ulnar bundle is a sensory branch and the radial one is a motor branch. The radial one goes around the hook of the hamate deep into the palm and then radially as the deep branch of the ulnar nerve does in the human hand. The radial bundle innervates ulnar intrinsic muscles (all intrinsic muscles except for thenar muscles and radial two lumbricals). The proximal-ward intraneural dissection revealed that most nerve fibers of this UABM come from the medial cord and some from the lateral cord, and that further proximally one half of fasciculi coming from the medial cord originates from the medial division (Eisler) of the middle trunk·C7 root and the other half from the lower trunk·C8 root. We are not sure that this branch of the median nerve innervating the ulnar intrinsic muscles of the hand is the common structure of the nervous system in the forelimb of the gorilla.