The brachialis (also brachialis muscle, Casserio`s muscle, latin: musculus brachialis) is a thick muscle of the upper arm located in the anterior region under the biceps brachii.
The brachialis originates from the anterior surface of the lower part of the humerus.
The brachialis inserts onto the tuberosity of the ulna.
The main function of the brachialis is flexion of the forearm.
The brachialis is innervated by the musculocutaneous nerve.