deltoid

Intrinsic muscle of the shoulder (scapulohumeral). Origin: 1) lateral 1/3 of the anterior border of the scapula 2) lateral & posterior border of the acromion 3) lower border of the spine of the scapula Insertion: -> lateral side or the shaft of the humerus (deltoid tuberosity) a little above the middle of the humerus Action: 1) abduction of the arm at the shoulder 2) flexion of the arm at the shoulder 3) extension of the arm at the shoulder 4) rotation of the arm at the shoulder 5) anterior, middle & posterior portions of the muscle act independently Innervation: -> axillary nerve (C5, C6) via brachial plexus

References

Stedman's Medical Dictionary 27th ed, Williams & Wilkins, Baltimore, 1999