The muscles of the arm

The Brachialis Muscle :

Origin : - the anteromedial and anterolateral aspects of the humerus - the borders of the humerus Insertion: - the ulnar tuberosity Actions : - flexion of the forearm on the arm - tension of the capsule of the shoulder joint (via fibers that attach on it) Innervation : - the musculocutaneous nerve (C5-C7)

The Coracobrachialis Muscle :

Origin : - the coracoid process Insertion : - the medial aspect of the humerus Actions : - flexion of the arm - adduction of the arm - lowers the shoulder (when the insertion on the coracoid process is fixed) Innervation : - the musculocutaneous nerve (C5-C7)

The Anconeus Muscle:

Origin : - the lateral epicondyle of the humerus Insertion : - the lateral border of the olecranon d of the ulna Actions : - extension of the forearm on the arm Innervation: - the radial nerve (C5-C8)

The Triceps Brachii Muscle :

Origin : - the long head: the infraglenoid tubercle of the scapula - the lateral head: the posterior aspect of the humerus, above the radial sulcus( also known as the musculospiral groove or the radial groove) - the medial head: the posterior aspect of the humerus, below the radial sulcus Insertion : - the olecranon of the ulna Actions : - extension of the forearm on the arm - extension of the arm - adduction of the arm (via its long head) Innervation : - the radial nerve (C5-C8)

The Biceps Brachii Muscle :

Origin : -the short head: on the coracoid process (common tendon of the biceps brachii and coracobrachialis muscles) -the long head: the supraglenoid tubercle of the scapula Insertion : -the radial tuberosity -from the muscle's tendon arises the bicipital aponeurosis which heads medially and distally inserting on the fascias of the arm and the forearm Actions: -flexion of the forearm on the arm -supination (at the beginning of the contraction, due to it's insertion on the radial tuberosity) -medial rotation of the arm (via its long head) Innervation : -the musculocutaneous nerve (C5-C7)