Final answer:
The anterior spinal artery supplies the anterior aspect of the spinal cord, and the basilar artery supplies the brain stem. Damage to the brain stem may affect lower cranial nerves involved in functions such as swallowing, speech, and tongue movement.
Step-by-step explanation:
The anterior spinal artery, which supplies blood to the anterior aspect of the spinal cord, is formed from the fusion of the two vertebral arteries. The anterior spinal artery runs along the anterior surface of the spinal cord. The brain stem is irrigated by branches of the basilar artery, which is formed from the fusion of the two vertebral arteries.
The cranial nerves that may be affected by damage to the brain stem include the lower cranial nerves such as the glossopharyngeal nerve (CN IX), vagus nerve (CN X), and hypoglossal nerve (CN XII). These nerves are involved in various functions such as swallowing, speech, and tongue movement.