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Deltoid – Functional Anatomy

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

Wikipedia entry for deltoid.


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Tony Preston has a practice in Atlanta, Georgia, where he sees clients. He has written and taught about anatomy, trigger points, and cranial therapies since the mid-90s.

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