Muscles of the arm and shoulder

The following session will cover muscles of the arm and shoulder, focusing on the anatomy, innovation, and functions of the major muscles of the arm and shoulder, including the biceps, triceps brachi brachialis, deltoid, and rotator cuff group. We will discuss how these muscles coordinate to enable complex movements such as lifting, pushing, pulling, and rotating the arm. Additionally, we will examine the role of the brachial plexus in muscle control and explore the clinical implications of muscle or nerve injury affecting upper limb function. These muscles facilitate a wide range of movement at the shoulder and elbow while also contributing to the strength and stability of the upper limb. The interplay between muscle anatomy, joint structure, and neural control enables lifting, pushing, pulling, and rotating of the arms. This overview will explore their anatomy, innovation, actions, and clinical relevance to illustrate how these systems collaborate for complex motion and stability. Let us first consider the principal muscles of the arm, the biceps brachi triceps brachi and brachialis. The biceps brachi in the anterior compartment, primarily flexes the elbow and supernates the forearm. Deep to it, the brachialis is the most powerful elbow flexor. Posteriorly, the triceps brachi extends the elbow, with its long head aiding shoulder extension. The biceps and brachialis are mainly innervated by the muscular cutaneous nerve and the triceps by the radial nerve.