The Common Carotid Artery

Course

The left and right common carotid arteries have different origins:

• Right common carotid artery – arises from the brachiocephalic trunk at the level of the sternoclavicular joint, within the root of the neck.
• Left common carotid artery – arises directly from the arch of the aorta as its second branch, within the superior mediastinum. It ascends anterior to the subclavian artery to reach the root of the neck, where it is level with its contralateral counterpart.

From this point, both arteries follow a similar course. They ascend through the neck within the carotid sheath, accompanied by the internal jugular vein and vagus nerve. Inferiorly, they lie lateral to the trachea, and more superiorly, lateral to the thyroid gland, larynx and pharynx. As they ascend, they are crossed anteriorly by the omohyoid muscle.

At the level of C4 (the superior border of the thyroid cartilage), each common carotid artery terminates by bifurcating into the internal carotid artery and external carotid artery. This occurs within the carotid triangle, where the carotid pulse can be palpated by compressing the artery against the transverse processes of the cervical vertebrae.

By TeachMeSeries Ltd (2026)

Fig 2
The course and relations of the common carotid artery in the neck.

Carotid Sinus & Carotid Body

The carotid sinus and carotid body are two specialised structures located near the bifurcation of the common carotid artery:

• Carotid sinus – a dilatation at the terminal part of the common carotid artery (or proximal internal carotid artery). It contains baroreceptors innervated by the glossopharyngeal nerve (CN IX), which detect changes in blood pressure. An increase in blood pressure results in reflex slowing of the heart rate and vasodilation.
• Carotid body – a small structure located posterior to the bifurcation of the common carotid artery. It acts as a chemoreceptor, detecting changes in blood oxygen levels. A decrease in oxygen concentration stimulates an increase in heart rate, blood pressure and respiratory rate.

Supply

The common carotid artery does not usually give rise to any vessels in the neck. Instead, it acts as a major conduit vessel, providing arterial supply to almost all structures of the head and neck via its two terminal branches:

• Internal carotid artery – supplies intracranial structures, including the brain (via the anterior circulation), as well as the orbit and retina
• External carotid artery – supplies extracranial structures, including the face, scalp, neck, and deeper structures such as the oral cavity, pharynx and larynx

Clinical Relevance

Carotid Artery Stenosis

Carotid artery stenosis refers to narrowing of the arterial lumen – most commonly due to atherosclerotic plaque formation. It typically occurs at the bifurcation of the common carotid artery, where blood flow becomes less streamlined. This creates areas of turbulent flow and reduced shear stress, which promote plaque deposition.

Stenosis at the bifurcation can reduce blood flow into both terminal branches. However, reduced flow in the internal carotid artery is of greatest clinical significance, as it supplies the brain and can result in transient ischaemic attack or stroke. In contrast, the external carotid artery supplies the face and scalp, where collateral circulation usually limits the impact of reduced flow.

Carotid artery stenosis is typically investigated using duplex ultrasound, with CT or MR angiography used for further assessment. Management depends on severity and symptoms, and includes medical therapy (e.g. antiplatelets and risk factor modification) or surgical intervention such as carotid endarterectomy.

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Fig 3
Carotid artery stenosis typically occurs at the birfucation of the common carotid artery due to its turbulent blood flow.