Deltoid

The deltoid muscle (m.deltoideus) is located superficially, directly under the skin, covers the shoulder joint from the lateral side, front, top and back, forms a characteristic roundness of the shoulder). This muscle is separated from the large pectoral muscle by the deltoid-pectoral furrow (sulcus deltoideopectoralis). The deltoid muscle has a pinnate structure and an extensive origin. It begins at the anterior margin of the lateral third of the clavicle, the outer edge of the acromion, on the awn of the scapula and the adjacent part of the subacute fascia. Accordingly, three parts of the deltoid muscle are distinguished: clavicular, acromial and scapular. Bunches of all three parts of the muscle converge on the outer surface of the humerus and attach to the deltoid tuberosity.

The unequal arrangement of the muscular bundles of individual parts of the deltoid muscle with respect to the shoulder joint, their different lengths and the way of attachment to the humerus determine the various directions of action of their force.

Under the deltoid muscle, between the deep plate of its fascia and the large tubercle of the humerus, there is a synovial podeltoide bag (bursa subdeltoidea).

Function of the deltoid muscle: individual parts of the muscle can contract, as well as the entire muscle. The anterior (clavicular) part of the muscle flexes the shoulder, while turning it to the inside, the raised arm drops down. The back (scapular) part unbends the shoulder, while turning it outward, the raised arm drops down. The middle (acromial) part of the muscle withdraws the arm. With the contraction of the entire muscle, she withdraws her arm to 70 °.

Innervation of the deltoid muscle: axillary nerve (CV-CVI).

Blood supply of deltoid muscle: posterior artery, surrounding humerus, pectoral artery.

[1], [2], [3]