What muscle is located in the upper arm and assists with shoulder abduction?

The muscle that is located in the upper arm and plays a key role in shoulder abduction is the deltoid. The deltoid muscle is shaped like an inverted triangle and covers the shoulder joint. It consists of three distinct parts: the anterior (front), lateral (middle), and posterior (back) fibers. The lateral fibers are specifically responsible for shoulder abduction, allowing the arm to move away from the body.

During shoulder abduction, particularly from about 15 to 90 degrees of movement, the deltoid muscle is vital for lifting the arm sideways. When the arm is raised, the deltoid contracts, which helps stabilize the shoulder joint and facilitates movement. This makes the deltoid essential for various activities that involve lifting the arm to the side or overhead.

Other muscles mentioned, while important for various functions, do not primarily assist in shoulder abduction. The trapezius is more involved in scapular movement and stabilization rather than direct arm abduction. The biceps brachii is primarily a flexor of the elbow and assists with shoulder flexion but does not contribute significantly to abduction. The coracobrachialis assists in flexing and adducting the arm but not in abduction. This anatomical