What nerve innervates the Deltoid?

• A. Axillary
• B. Suprascapular
• C. Median
• D. Musculocutaneous

Answer: (A)

The Deltoid muscle is innervated by the axillary nerve. This nerve comes from the posterior cord of the brachial plexus (C5–C6) and travels through the quadrangular space to reach the deltoid, giving motor input that enables shoulder abduction after the initial 15 degrees. It also carries sensory fibers to the skin over the superolateral arm via the superior lateral cutaneous branch.

Other nerves listed do not supply the deltoid: the suprascapular nerve targets the supraspinatus and infraspinatus; the median nerve supplies most of the forearm flexors and some hand muscles; the musculocutaneous nerve innervates the anterior arm muscles. Therefore, the axillary nerve is the correct innervation for the deltoid.