The main artery in your neck is the carotid artery. You have two of them, one running up each side of your neck, and together they supply about 80% of the blood flow to your brain. A second, smaller pair of arteries called the vertebral arteries also runs through your neck, tucked inside the bones of your spine, delivering the remaining 20%.
The Common Carotid Artery
Each common carotid artery travels from your upper chest toward your skull. They don’t start in the same place, though. The left one branches directly off the aorta (the body’s largest artery, coming straight from the heart), while the right one branches off a shorter vessel called the brachiocephalic trunk. Despite the different origins, both arteries follow the same path upward along either side of your neck.
Roughly at the level of your third cervical vertebra, which sits behind the upper edge of your Adam’s apple, each common carotid splits into two branches: the internal carotid artery and the external carotid artery. This split point is called the carotid bifurcation. While anatomy textbooks often place it at the C3-C4 level, the exact spot varies from person to person and can sit as low as C6 or as high as C2.
Internal Carotid: Blood Supply to the Brain
The internal carotid artery continues straight up through your neck and enters your skull through an opening in the bone at its base. Once inside, it branches into smaller arteries that feed your brain and eyes. Its major branches include the ophthalmic artery (supplying your eyes), the middle cerebral artery (covering a large portion of the brain’s surface), and the anterior cerebral artery (feeding the front of the brain). Because the internal carotid delivers so much of the brain’s blood, blockages here are a leading cause of stroke.
External Carotid: Blood Supply to the Face and Scalp
The external carotid artery takes a different path. It travels upward along the side of your neck toward your ear, sending off eight branches along the way. These branches supply blood to your thyroid gland, tongue, face, scalp, jaw, and the back of your head. If you’ve ever noticed heavy bleeding from a facial cut, it’s because this network of arteries keeps the tissues of your face and scalp richly supplied with blood.
Vertebral Arteries: The Backup Route
Your vertebral arteries are less well known but equally important. One runs on each side of your neck, threaded through small openings in the vertebrae of your cervical spine. They enter these bony tunnels at the C6 vertebra (about mid-neck) and exit at C2, near the top of the spine, before curving across the uppermost vertebra and entering the skull.
Once inside the skull, the two vertebral arteries merge into a single vessel called the basilar artery. This system, called the vertebrobasilar system, feeds the brainstem, cerebellum, and the back of the brain. These areas control balance, coordination, vision, and basic life functions like breathing. So while the vertebral arteries carry only about 20% of the brain’s blood supply, the structures they feed are critical.
The Carotid Pulse and Built-In Sensors
The carotid artery is the one you’re feeling when you press two fingers against the side of your neck to check your pulse. The best spot is alongside your windpipe, roughly at the midpoint of your neck, where the artery runs close to the surface. This is a common place for paramedics and first responders to check for a heartbeat because the carotid is large and easy to locate.
Right at the bifurcation point, where the common carotid splits in two, sits a small structure called the carotid sinus. It contains pressure sensors that constantly monitor your blood pressure. When your blood pressure drops, these sensors trigger your heart to beat faster and your blood vessels to tighten, bringing the pressure back up. They also influence your breathing rate. Nearby, a tiny cluster of cells called the carotid body monitors oxygen and carbon dioxide levels in your blood. Together, these sensors act as a real-time feedback system that keeps your brain well supplied with oxygenated blood.
This is why pressing too firmly on the side of your neck can occasionally make you feel lightheaded. The pressure tricks those sensors into thinking blood pressure is too high, and they respond by slowing your heart rate.
Carotid Artery Disease
The most common problem affecting the neck arteries is carotid artery disease, where fatty deposits gradually narrow the inside of the vessel. This is the same process that clogs coronary arteries in heart disease, and it tends to develop at the bifurcation point where blood flow is naturally turbulent.
The tricky part is that carotid artery disease often causes no symptoms until the narrowing becomes severe. In some cases, the first warning sign is a transient ischemic attack, sometimes called a mini-stroke. During a TIA, you might experience sudden weakness or numbness on one side of the body, difficulty speaking, or vision loss, but symptoms typically resolve within an hour. A TIA is a serious warning that a full stroke could follow. In other cases, a doctor might detect a whooshing sound called a bruit when listening to your neck with a stethoscope during a routine exam.
Risk factors are the same ones that drive heart disease: high blood pressure, high cholesterol, smoking, diabetes, and aging. Imaging tests, typically an ultrasound of the neck, can confirm how much narrowing is present and guide treatment decisions.