The deltoid muscle is a lateral muscle of the shoulder. Its origin are divided in three parts (two parts in horses because there is no acromion):
- Scapular part: from scapular spine to the deltoid tuberosity
- Acromial part: from acromion to deltoid tuberosity
- Clavicular part: This part of the deltoid muscle is well present in human shoulder, but due to the reduction of the clavicle, in domestic animals, this part of the deltoid is included as a part of the brachiocephalic muscle called the cleidobrachial muscle. So in the Vth edition of the NAV, the cleidobrachial muscle is described as the "Clavicular part of deltoid", but included in the muscles of the neck section as a part of the brachiocephalic muscle !
Origin: Opalescent aponeurosis and scapular spine and acromion process of the scapula.
Insertion: Deltoid tuberosity of the humerus.
Action: Flexion of the shoulder joint, lifting of the humerus.
Text by Antoine Micheau, MD - Copyright IMAIOS