24.23: The Arch of Aorta
The coronary arteries, originating from the ascending aorta, bifurcate from two sinuses located within the ascending aorta. Positioned just above the aortic semilunar valve, these sinuses house essential aortic baroreceptors and chemoreceptors, crucial for maintaining cardiac function. The left coronary artery and the right coronary artery branch off from the left posterior and anterior aortic sinuses, respectively.
Encircling the heart, the coronary arteries form a ring-like structure before splitting into branches that deliver blood to heart tissues. The aortic arch gives rise to three primary branches: the brachiocephalic artery, the left common carotid artery, and the left subclavian artery, all classified as elastic arteries due to their proximity to the heart. The brachiocephalic artery, unique to the right side, bifurcates into the right subclavian artery and the right common carotid artery. In contrast, the left subclavian and left common carotid arteries branch independently from the aortic arch, following a similar distribution pattern to their right counterparts.
The subclavian arteries supply blood to the arms, chest, shoulders, back, and the central nervous system. Each artery further divides into three major branches: the internal thoracic artery, the vertebral artery, and the thyrocervical artery. The internal thoracic artery delivers blood to the thymus, pericardium, and anterior chest wall, while the vertebral artery, traveling through the vertebral foramen and foramen magnum, supplies blood to the brain and spinal cord.
The common carotid artery bifurcates into the internal and external carotid arteries. The right common carotid artery stems from the brachiocephalic artery, while the left common carotid artery stems directly from the aortic arch. The external carotid artery supplies structures such as the face, lower jaw, neck, esophagus, and larynx. The internal carotid artery forms a carotid sinus, housing carotid baroreceptors and chemoreceptors, which are vital for maintaining cardiovascular homeostasis.
The blood supply to the human brain relies primarily on the internal carotid arteries and the vertebral arteries. Interruption of blood flow to the brain, even momentarily, can cause a transient ischemic attack (TIA) or mini-stroke, potentially leading to loss of consciousness or temporary neurological function loss. Prolonged interruption can result in irreversible brain damage or stroke.
The internal carotid artery continues through the carotid canal of the temporal bone, entering the base of the brain via the carotid foramen and splitting into several branches. These include the anterior cerebral artery, which supplies blood to the frontal lobe of the cerebrum, and the middle cerebral artery, which supplies blood to the temporal and parietal lobes. The ophthalmic artery, another significant branch, supplies blood to the eyes.
The anterior cerebral arteries form an anastomosis called the anterior communicating artery. Together with the initial segments of the anterior cerebral arteries, they form the anterior portion of the arterial circle, also called the Circle of Willis. The posterior portion is formed by the posterior communicating arteries branching off from the posterior cerebral artery, which arises from the basilar artery. This artery provides blood to the posterior region of the cerebrum and brainstem. The basilar artery begins where the two vertebral arteries meet and sends branches to the cerebellum and brainstem, eventually merging into the posterior cerebral arteries.
