Peripheral nerves of the brachial plexus with their distribution to the muscles of the pectoral limb in the captive African Striped Ground Squirrel (Xerus erythropus)

This research provides a detailed description of the gross morphology of the brachial plexus with its peripheral nerve distribution to the muscles of the pectoral limb in the African Striped Ground Squirrel (ASGS). Six (6) adult ASGSs of both sexes were used for this study. The squirrels were euthanised using ketamine hydrochloride at a dose of 60 - 80 mg/kg intramuscularly. They were perfused intracardially with 10 % formalin and fixed in the same solution for three days. The muscles were dissected along the intermuscular septae, and the nerves supplying them were identified and photographed. The vertebral column was opened by laminectomy to expose the cervical and thoracic nerve roots. The last four cervical nerves and the first two thoracic nerves arose from the cervical and thoracic segments, respectively, of the spinal cord of the ASGS by means of dorsal and ventral roots. The cervical and thoracic nerves are divided into dorsal and ventral rami just after exiting the intervertebral foramen. The ventral rami of the last four cervical nerves (C5, C6, C7, and C8) and the first two thoracic nerves (T1 and T2) are interconnected to form the brachial plexus. The peripheral nerves of the brachial plexus, including the subscapular nerve, suprascapular nerve, pectoral nerve, axillary nerve, radial nerve, musculocutaneous nerve, ulnar nerve, median nerve and thoracodorsal nerve, supplied the subscapularis, supraspinatus, pectoralis, teres major, triceps brachii, coracobrachialis, flexor carpi ulnaris, flexor carpi radialis and latissimus dorsi, respectively. The peripheral branches of the brachial plexus supply innervation to the muscles of the pectoral limb. The increased number of spinal nerves that constituted the brachial plexus of the ASGS from this study points to increased versatility of actions of the pectoral limb of the ASGS in climbing, wide jump between tree branches and digging.