Deltoid Muscle: Origin, Insertion & Action

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  • 0:04 Deltoid Muscle
  • 1:01 Origin & Insertion
  • 1:46 Action
  • 2:21 Lesson Summary
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Lesson Transcript
Instructor: Dan Washmuth

Dan has taught college Nutrition, Anatomy, Physiology, and Sports Nutrition courses and has a master's degree in Dietetics & Nutrition.

The shoulder joint is one of the most mobile joints in the body, and this joint is controlled primarily by the deltoid muscle. If you want to learn all about this amazing muscle, be sure to check out this lesson!

Deltoid Muscle

Let's play a quick game of Simon Says.

  1. Simon says to lift your arms out to the sides.
  2. Simon says to raise your arms to the front.
  3. Simon says to raise your arms to the back.
  4. Now move your arms around in circles.

If you did step #4, you're out because Simon didn't say!

This corny little game of 'Simon Says' begins to show the impressive mobility of the shoulder joint, which is one of the most mobile joints in the body. The shoulder joint allows your arm to move in almost any direction, and many of these movements around the shoulder joint are controlled by the deltoid muscle.

The deltoid muscle is the large, triangular-shaped muscle of the shoulder. This muscle actually gets its name from the Greek letter 'delta,' which is in the shape of a triangle, a reference to the structure of this muscle. The deltoid muscle is divided into three main sections, which includes the anterior (front), medial (middle), and posterior (back) sections.

Origin & Insertion

Since the deltoid muscle is divided into three different sections, this muscle has multiple points of origin. This chart describes these points of origin.

Section of Deltoid Point of Origin
Anterior The lateral (outside) portion of the clavicle, which is also known as the collarbone.
Medial The acromion process and the spine of the scapula (shoulder blade). The acromion process is a bony prominence at the top of the shoulder blade, while the spine is a ridge or plate also at the top of the shoulder blade.
Posterior Spine of the scapula.

Each section of the deltoid muscle inserts at the same location, which is the deltoid tuberosity of the humerus, or the long bone in the upper arm. The deltoid tuberosity is a triangular-shaped area on the humerus, located about halfway down the bone.


As it has already been discussed, and shown by the game of Simon Says at the beginning of the lesson, the deltoid muscle is responsible for many different actions of the arm around the shoulder joint. Each different section of the deltoid moves the arm in different directions.

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