When it contracts, it pulls the muscle to rotate: different fibres to do different activities, innervation: lat. and med. Pectoral nerves: pec minor is innervated by medial pectoral nerve. Starts to compress the structure within the compartment: it could be nerves. The key to hold humerus tightly to the joint: insertion: tuberosity of radius and bicipital aponeurosis of forearm, aponeurosis is a flatten tendon. Part of the muscle is contracted and balled up: biceps brachii cross shoulder joint and elbow joint. Explain how you would test the nerve function for each muscle: the medial fibre of deltoid is straight up and down when the shoulder is resting, both supraspinatus and the deltoid muscles cause abduction. Supraspinatus initiates abduction while deltoid takes over when the limb is at approximately 15 degrees. When the arm is fully adducted, the pull of deltoid is upwards.