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Deltoid

Other Terms: Musculus deltoideus, Muscle deltoïde

Muscle parts

Clavicular part; Acromial part; Spinal part

Latin name

Musculus deltoideus

Latin muscle parts

Pars clavicularis; Pars acromialis; Pars spinalis

Group

Shoulder joint muscle – shoulder cap

Etymology

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.”

Origin

Spine and acromion of the scapula and lateral part of the clavicle

Insertion

Deltoid tuberosity of the humerus and the brachial fascia

Action

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.

Nerve supply

Axillary nerve (C5 and C6)

Blood supply

Thoraco-acromial artery via the deltoid and acromial branches; anterior circumflex humeral artery; posterior circumflex humeral artery; deltoid branch of the brachial profunda artery.

Latin

Musculus deltoideus

French

Muscle deltoïde

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