Clavicular part of deltoid muscle

At a glance

English

Clavicular part of deltoid muscle

Latin (TA2)

Pars clavicularis musculi deltoidei

System

Muscle

Region

Upper limb

Side

Paired, left and right

About the clavicular part of deltoid muscle

The deltoid forms the rounded cap of the shoulder and is divided by its origins into three parts. The clavicular part, also called the anterior deltoid, makes up the front of the muscle. It lies just lateral to the clavicular head of pectoralis major, and the two are separated only by a narrow furrow, the deltopectoral groove, in which the cephalic vein climbs to the infraclavicular fossa. In some people the two muscles are partly fused here.

Its fibres arise from the outer third of the clavicle, along its front edge and upper face. They pass downward, backward and outward over the front of the shoulder joint and converge with the other parts of the muscle on the deltoid tuberosity, halfway down the outer side of the humeral shaft. Unlike the middle part, the front fibres are arranged in long, nearly parallel bundles, giving a good range of movement.

Because it passes in front of the shoulder, the clavicular part raises the arm forward (flexion) and turns it inward (medial rotation), working with the clavicular head of pectoralis major. It also draws the raised arm across the front of the body in horizontal adduction and helps the middle fibres to raise the arm sideways once abduction is under way. It is active in pushing, pressing a weight overhead and lifting objects in front of the body. Like the rest of the deltoid it is supplied by the axillary nerve, carrying fibres from the fifth and sixth cervical segments, and its blood comes mainly from the deltoid branch of the thoracoacromial artery, with the anterior circumflex humeral artery.

The deltopectoral groove alongside this part is the usual surgical route to the front of the shoulder joint, and the cephalic vein is a guide to the interval. Weakness of the front fibres, as in axillary nerve injury, makes it harder to lift the arm forward, and wasting changes the shape of the front of the shoulder. The cephalic vein in the groove is sometimes used for placing pacemaker leads.

Attachments, action and supply

Origin

Outer third of the clavicle, on its front edge and upper face.

Insertion

Deltoid tuberosity on the lateral surface of the humeral shaft.

Action

Flexes and medially rotates the arm at the shoulder; assists horizontal adduction and abduction.

Nerve supply

Axillary nerve (C5, C6).

Blood supply

Deltoid branch of the thoracoacromial artery and the anterior circumflex humeral artery.