Superior lateral cutaneous nerve of arm

The superior lateral cutaneous nerve of arm (or superior lateral brachial cutaneous nerve) is the continuation of the posterior branch of the axillary nerve, after it pierces the deep fascia. It contains axons from C5-C6 ventral rami.

Structure
It sweeps around the posterior border of the deltoideus and supplies the skin over the lower two-thirds of the posterior part of this muscle, as well as that covering the long head of the triceps brachii.