What is the innervation of shoulder abduction?

Shoulder abduction is primarily innervated by two muscles, the supraspinatus and the deltoid.

Supraspinatus

The supraspinatus muscle, which is located on the top of the shoulder, is innervated by the suprascapular nerve. The suprascapular nerve arises from the roots of the fifth (C5) and sixth (C6) cervical nerves and travels through the supraspinous fossa to reach the supraspinatus muscle.

Deltoid

The deltoid muscle is innervated by the axillary nerve. The axillary nerve arises from the roots of the fifth (C5) and sixth (C6) cervical nerves and travels through the shoulder joint to reach the deltoid muscle.