The carotid arteries are major blood vessels located in the neck, responsible for supplying oxygen-rich blood to the head, including the brain. They are a significant component of the body’s circulatory system, ensuring that vital organs receive the blood they need to function properly. Understanding their location and role provides insight into the body’s intricate network for blood distribution.
General Location of Carotid Arteries
The carotid arteries are situated on each side of the neck. These arteries begin their journey in the upper chest, just below the neck, and extend upwards towards the skull. They run vertically through the neck, positioned laterally to the trachea, or windpipe, and medial to the sternocleidomastoid muscle, which is a large muscle extending from behind the ear to the collarbone.
Specifically, the right common carotid artery originates from the brachiocephalic trunk, while the left common carotid artery branches directly from the aortic arch in the chest. Both common carotid arteries ascend through the neck, typically without branching, until they reach the level of the upper border of the thyroid cartilage, around the fourth cervical vertebra (C4). At this point, each common carotid artery divides into two main branches, forming a bifurcation.
Internal and External Carotid Arteries
The common carotid artery on each side branches into two distinct arteries: the internal carotid artery and the external carotid artery. These two branches have different paths and supply blood to different regions of the head and neck. The internal carotid artery (ICA) travels deeper into the neck and enters the skull. It does not give off any branches in the neck itself.
Once inside the skull, the internal carotid artery supplies blood to the brain and the eyes. This artery is a primary component of the anterior circulation system, which provides blood to the forebrain. In contrast, the external carotid artery (ECA) travels upward along the side of the neck, supplying blood to the face, scalp, and other structures external to the brain. It gives rise to several branches, including the facial artery, lingual artery, and superior thyroid artery, which provide blood to areas such as the lips, cheeks, jaws, tongue, and thyroid gland.
Essential Role in Circulation
The carotid arteries play a crucial role in the body’s circulatory system by delivering oxygenated blood to the brain and other parts of the head and neck. This continuous supply is necessary because the brain is an organ with high metabolic activity, consuming about 20% of the body’s oxygen and 15% of its glucose, despite making up only about 2% of the body’s weight. The brain cannot store oxygen or glucose effectively, making a constant and stable blood supply paramount for its proper function.
Blood flow to the brain is approximately 750 milliliters per minute in an adult human, representing about 15% of the body’s cardiac output. If the brain is deprived of oxygen for even a few minutes, it can lead to damage. The cerebral circulatory system has mechanisms, such as autoregulation, to maintain consistent blood flow despite changes in blood pressure. This ensures that the brain receives the necessary oxygen and nutrients to sustain its complex activities, from cognitive functions to controlling bodily processes.
Finding Your Carotid Pulse
Locating your carotid pulse can provide a quick assessment of your heart rate. The carotid pulse is typically felt in the neck, situated between the windpipe and the large sternocleidomastoid muscle. To find it, gently place the pads of your index and middle fingers on one side of your neck, in the groove alongside your windpipe. Apply gentle pressure until you feel a rhythmic pulsation.
It is important to use only light pressure, as pressing too hard can reduce blood flow or stimulate a nerve, which might slow the heart rate. Never attempt to palpate both carotid arteries simultaneously, as this action can restrict blood flow to the brain and potentially cause dizziness or fainting. Count the beats for 15 seconds and then multiply by four to determine your heart rate per minute.