This initial part of abduction is produced by the supraspinatus muscle. ORIGIN Lateral third of clavicle, acromion, spine of scapula to deltoid tubercle : INSERTION Middle of lateral surface of humerus (deltoid tuberosity) ACTION Abducts arm, anterior fibers flex and medial rotate, posterior fibers extend and lateral rotate : NERVE Axillary nerve (C5, 6) … It originates from the lateral end of the clavicle, the acromion of the scapula at the top of the shoulder, and the spine of the scapula. Origin & Insertion Since the deltoid muscle is divided into three different sections, this muscle has multiple points of origin. However, it can only do so, when the arm is already abducted beyond fifteen degrees. Deltoid Muscle - Anterior and Middle Heads. DELTOID. Retraction of the The origin and insertion of the deltoid muscle . It inserts on the deltoid tuberosity of the humerus. 1. The deltoid consists three sets of fibers: anterior, middle, and posterior. The clavicular and scapular spinal fibers of the muscle guide the arm through the abduction motion. Muscle Anatomy of the Middle Deltoid. The deltoid muscle (acromial part) is the principal abductor of the arm at the glenohumeral joint. The Deltoid muscle (derived its name from the Greek letter delta) is a large, triangular muscle occupying the upper arm and the shoulder giving it this rounded shape. This chart describes these points of origin. Origin: Lateral border of the acromion process of the scapula Insertion: Deltoid tuberosity on the lateral surface of the proximal humeral shaft Actions: Abduction of the arm at the shoulder Innervation: Axillary nerve (C5, C6) Blood Supply: Posterior humeral circumflex Primary Actions of the Middle Deltoid.