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Other Terms: Musculus deltoideus, Muscle deltoïde
Clavicular part; Acromial part; Spinal part
Latin muscle parts
Pars clavicularis; Pars acromialis; Pars spinalis
Shoulder joint muscle – shoulder cap
In English, this muscle’s name is the triangle-shaped muscle. The term deltoid is a conjugation of the Greek terms delta, the fourth letter of the Greek alphabet, which resembles a triangle and the word eidos (oid) meaning “shape or form.”
Spine and acromion of the scapula and lateral part of the clavicle
Deltoid tuberosity of the humerus and the brachial fascia
Flexion abduction, and extension of the humerus – older reports suggest that the deltoid functions in all movements of the arm — flexion, extension, abduction, adduction, medial rotation, and lateral rotation. Recent EMG evidence demonstrates that the deltoid participates little if at all in lateral and medial rotation of the humerus and not at all in adduction. All parts of the muscle are active during flexion, extension, and abduction. The anterior fibers are most active during flexion of the humerus being slightly active during abduction. The lateral fibers are most active during abduction but also participate significantly in both flexion and extension. The posterior fibers show the strongest activity during extension and fire inconstantly in abduction.
Axillary nerve (C5 and C6)
Thoraco-acromial artery via the deltoid and acromial branches; anterior circumflex humeral artery; posterior circumflex humeral artery; deltoid branch of the brachial profunda artery.