The left subclavian artery is a major blood vessel that branches off from the aortic arch in the chest. It supplies oxygenated blood to the left arm, neck, and parts of the brain. This artery is crucial for maintaining proper blood flow to these areas. Located beneath the collarbone, the left subclavian artery runs laterally and then curves around the first rib. It gives rise to several important branches, including the vertebral artery, which supplies blood to the brain, and the internal thoracic artery, which supplies the chest wall.