The anterior division of the lower trunk forms the medial cord. All 3 posterior divisions from each of the 3 cords all unite to form the posterior cord. The cords are named according to their position relative to the axillary artery. Terminal Branches are mixed nerves containing both sensory and motor axons. Musculocutaneous nerve is derived from the lateral cord.
Axillary nerve is derived from the posterior cord.
Motor innervation is deltoid and teres minor muscles that act on the shoulder joint. Sensory innervation is from the skin just below the point of the shoulder. Radial nerve is also derived from the posterior cord. Sensory innervation is from the skin on the dorsum of the hand on the radial side. Usually leads to loss of nerve function Entrapment Nerve passing though a muscle or defined space Musculocutaneous nerve passing through coracobrachialis muscle Carpal Tunnel Syndrome Diminished function but no total loss Spinal Cord lesion All muscles supplied by spinal nerves below the site of the lesion are paralyzed Loss of sensation below the site of the lesion Lesions are referred to as the lowest portion of the spinal cord that functions a C5 spinal cord lesion means all spinal nerves below the 5th.