The Deltoid is a three-headed muscle that forms the rounded bulk of the shoulder. It is named after the Greek letter delta, which it resembles.
Brief Anatomy Overview
Origin
lateral third of the clavicle, acromion and spine fo the scapula
Insertion
deltoid tuberosity of the humerus
Function
abduction of the humerus, strongest in slight medial rotation
The deltoid is key in stabilizing the shoulder in the glenoid fossa to reduce strain on the rotator cuff muscle and prevent subluxation or dislocation of the humeral head.
Nerve
Axillary Nerve C5-C6
Anterior
Origin
lateral third of the clavicle
Insertion
deltoid tubercle of the humerus
Function
horizontal flexion of the humerus
assists with medial rotation
Middle
Origin
acromion of the scapula
Insertion
deltoid tubercle of the humerus
Function
abduction of the humerus
Posterior
Origin
spine of the scapula
Insertion
deltoid tubercle of the humerus
Function
extends the humerus when it is in horizontal flexion (in front of the body)
assists in external rotation of the humerus
abduction of the humerus
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Tony Preston has a practice in Atlanta, Georgia, where he sees clients. He has written materials and instructed classes since the mid-90s. This includes anatomy, trigger points, cranial, and neuromuscular.
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