Muscles of the Shoulder & Arm
- Biceps brachii muscle originates as two head. The long head appears as a tendon from the supraglenoid tubercle of the scapula and passes over the head of the humerus, deep to the joint capsule and enters the intertubercular sulcus where it is held in position by the transverse humeral ligament. The short head of biceps brachii arises from the coracoid process of the scapula and joins the long head further down the humerus. The biceps brachii inserts primarily as a tendon into the radial tuberosity of the forearm and into the fascia on the medial part of the forearm. Biceps brachii is the primary flexor of the forearm; it also supinates the forearm and weakly flexes the arm at the shoulder.
- Coracobrachialis muscle, together with the short head of biceps brachii muscle, originates from the tip of the coracoid process. It inserts on to the middle third of the medial surface and border of the humerus. Coracobrachialis weakly adducts the arm and aids in stabilizing the humerus.
- Triceps brachii muscle has three heads. The long head originates from the infraglenoid tubercle of the scapula; the lateral head from the upper half of the posterior surface of the shaft of the humerus and the medial head from the posterior surface of the lower half of the shaft of the humerus. All of these heads pass vertically down the arm to insert on the olecranon of the ulna. The triceps is the primary extensor of the forearm at the elbow joint. Because the long head crosses the glenohumeral joint, it can also extend and adduct the humerus.