Corpus: Brachialis muscle

The brachialis muscle originates at the anterior margin and the anterior surface of the distal half of the humerus as well as at the intermuscular brachial septum medially and – with smaller parts – laterally. The muscle fibers converge to form a thick tendon that inserts on the ulnar tuberosity and on the anteroinferior surface of the coronoid process of the ulna.

The brachialis muscle is innervated by the musculocutaneous nerve from the brachial plexus (segments: C5 - C6 possibly with parts from C7). The radial nerve innervates a smaller part of the muscle. These fibers are probably used for proprioception.

Together with the biceps muscle, the brachialis muscle is responsible for flexion (bending) of the forearm in the elbow joint.

As it inserts at the ulna, the brachialis muscle, in contrast to the biceps muscle, flexes the forearm in both the pronated and supinated position. As it only pulls across one joint, its influence on the flexion of the forearm is stronger than that of the biceps. It is therefore the strongest flexor in the elbow joint.