Nerve · Upper arm

Superior lateral cutaneous nerve of the arm

Nervus cutaneus brachii lateralis superior

The axillary nerve's only sensory branch, and the only skin the axillary nerve reaches. After the parent nerve has wound round the surgical neck of the humerus and supplied deltoid and teres minor, this branch curls round the back border of deltoid to surface over the muscle's lower half. The patch it covers is small, round and famous — the 'regimental badge' area on the outer shoulder, where an army badge would sit. That a nerve supplying a large and powerful muscle should reach only a coin-sized field of skin is a good illustration of how loosely motor and sensory territories map onto each other.