The brachialis muscle is a spindle-shaped muscle which lies deeply under the biceps brachii. It arises from the anterior surface of distal half of humerus. Then it travels downwards, stretching over the elbow-joint and fusing with its capsule, to be inserted into the tuberosity of ulna.
Action
When it contracts, the brachialis muscle flexes the forearm, pulling it towards the anterior side of arm. In this action, it works in unison (together) with the biceps brachii. It also stretches the capsule of the elbow-joint.
Innervation
It is innervated by a branch of the musculocutaneous nerve (C5-C6).
Blood Supply
This strong muscle receives oxygenated blood from the ulnar collateral, radial recurrent, and the brachial artery.
Below, picture of the brachialis muscle on the place it occupies on the arm and forearm. The biceps brachii and muscles of the forearm are absent.
