Deltoid
Latin: M. deltoideus sinistra
Location: Shoulder
Paired structure: one on the left and one on the right side of the body.
View the deltoid in 3DOrigin
Lateral third of the clavicle (anterior head), acromion (middle head), spine of the scapula (posterior head).
Insertion
Deltoid tuberosity of the humerus.
Action
Abducts the arm beyond 15° (after supraspinatus initiates); anterior head flexes and medially rotates; posterior head extends and laterally rotates the shoulder.
Nerve supply
Axillary nerve (C5–C6).
Blood supply
Posterior circumflex humeral artery; deltoid branch of the thoracoacromial artery.
Clinical relevance
Axillary nerve injury after shoulder dislocation wastes the deltoid and numbs the 'regimental badge' area. The muscle is the standard site for intramuscular injections — its paralysis flattens the shoulder's rounded contour.
Educational anatomy reference, not medical advice. About this content.