Skip to main content

Unfortunately we don't fully support your browser. If you have the option to, please upgrade to a newer version or use Mozilla Firefox, Microsoft Edge, Google Chrome, or Safari 14 or newer. If you are unable to, and need support, please send us your feedback.

Publish with us
Deltoid Muscle (Left)
Muscular System

Deltoid Muscle (Left)

Musculus deltoideus

Read more

Quick Facts

Origin: Lateral one third of clavicle, acromion and spine of scapula.

Insertion: Deltoid tuberosity of humerus.

Action: Abducts, flexes, extends, and medially and laterally rotates arm at glenohumeral (shoulder) joint.

Innervation: Axillary nerve (C5-C6).

Arterial Supply: Acromial and deltoid branches of thoracoacromial artery, anterior and posterior circumflex humeral and subscapular arteries, deltoid branch of deep brachial artery.

Complete Anatomy
The world's most advanced 3D anatomy platform
Try it for Free


The clavicular part of the deltoid muscle originates from the anterosuperior aspect of the lateral one third of the clavicle. The acromial part originates from the lateral aspect of the acromion of the scapula. The scapular spinal part originates from the inferior aspect of the spine of the scapula.


The fibers of the deltoid muscle travel inferolaterally and converge to a single tendon. This tendon is short, thick and inserts onto the deltoid tuberosity of the humerus.

Key Features & Anatomical Relations

The deltoid muscle is the thick triangular muscle that gives the shoulder its rounded contour. It is composed of three heads:

- Aa clavicular part, which is the anterior unipennate portion;

- an acromial part, which is the middle multipennate portion;

- a scapular spinal part, which is the posterior unipennate portion.

The deltoid muscle is located:

- superficial to the glenohumeral (shoulder) joint, the proximal tendons of the biceps brachii and triceps brachii muscles, and the axillary nerve;

- deep to the deltoid fascia and the superior lateral brachial cutaneous nerve;

- lateral to the pectoralis major, trapezius and infraspinatus muscles.

Actions & Testing

The deltoid muscle is involved in multiple actions:

- abducts the arm at the glenohumeral (shoulder) joint when the acromial part contracts individually;

- flexes and medially rotates the arm at the glenohumeral joint when the clavicular part contracts individually;

- extends and laterally rotates the arm at the glenohumeral joint when the scapular spine part contracts individually.

The deltoid muscle can be tested by abducting the arm beyond the 30° position, against resistance, during which it can be seen and palpated (Standring, 2016).

List of Clinical Correlates

- Site for intramuscular injection


Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.

Learn more about this topic from other Elsevier products

Deltoid Muscle

ScienceDirect image

The subacromial bursa is located between the deep surface of the deltoid muscle, the superficial surface of the subscapularis, and the tendon of the long head of the biceps and is comprised of subacromial and subdeltoid portions.

Explore on ScienceDirectopens in new tab/window

Deltoid: What Is It, Location, Function, and More

Osmosis image

The deltoid muscle is a large, triangular-shaped muscle that lies superficially to other muscles of  the shoulder and is responsible for forming the shoulder’s rounded contour

Explore on Osmosisopens in new tab/window

Complete Anatomy

The world's most advanced 3D anatomy platform

Complete Anatomy