The Deltoid Muscle: Anatomy, Function, and Origin
An Overview of the Deltoid Muscle
The deltoid muscle is the primary muscle group that forms the rounded contour of the human shoulder. It is a large, triangular muscle that originates from the clavicle, acromion, and spine of the scapula. The deltoid muscle inserts into the deltoid tuberosity of the humerus, and its primary function is to abduct, flex, and extend the arm at the shoulder joint.
Parts of the Deltoid Muscle
The deltoid muscle consists of three distinct parts, each with a unique origin:
- Anterior deltoid: Originates from the anterior surface of the clavicle.
- Middle deltoid: Originates from the acromion process of the scapula.
- Posterior deltoid: Originates from the spine of the scapula.
1. Anterior Deltoid
The anterior deltoid is the smallest and most superficial of the three deltoid parts. It originates from the anterior surface of the clavicle and inserts into the anterior surface of the humerus. Its primary function is to flex the arm at the shoulder joint.
2. Middle Deltoid
The middle deltoid is the largest of the three deltoid parts. It originates from the acromion process of the scapula and inserts into the lateral surface of the humerus. Its primary function is to abduct the arm away from the body at the shoulder joint.
3. Posterior Deltoid
The posterior deltoid is the deepest of the three deltoid parts. It originates from the spine of the scapula and inserts into the posterior surface of the humerus. Its primary function is to extend the arm backward at the shoulder joint.
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