The vertebral arteries are major blood vessels that supply oxygenated blood to the brain and spinal cord. They originate from the subclavian arteries and travel upward through the cervical vertebrae, entering the skull through the foramen magnum. Once inside the skull, the two vertebral arteries merge to form the basilar artery, which further branches into the posterior cerebral arteries. This vascular system is crucial for maintaining proper brain function and overall neurological health.