Common carotid artery

Where do the common carotid arteries start?

The right common carotid arises from the brachiocephalic artery in the neck. The left arises straight from the aortic arch in the thorax. (StatPearls, Head and Neck: Carotid Arteries)

In the neck, each climbs from behind its sternoclavicular joint inside the carotid sheath, behind the sternocleidomastoid muscle. (StatPearls, Head and Neck: Carotid Arteries)

The carotid sheath holds the common carotid artery, the internal jugular vein and the vagus nerve, with deep cervical lymph nodes along the vein. (StatPearls, Head and Neck, Anterior: Common Carotid Arteries, Head and Neck: Carotid Arteries and Head and Neck: Internal Jugular Vein)

Where does the common carotid artery divide?

Each divides at the upper border of the thyroid cartilage, usually at the level of the fourth or fifth cervical vertebra, into the external and internal carotid arteries. (StatPearls, Head and Neck: Carotid Arteries)

The external carotid supplies the face and neck. The internal carotid passes through the carotid canal of the temporal bone to reach the brain. (OpenStax A&P 2e, 20.5; StatPearls, Head and Neck: Carotid Arteries and Head and Neck: Internal Carotid Arteries)

What does the common carotid artery do?

Its internal carotid branch carries blood to the brain. With the vertebral arteries, which come off the subclavian arteries, the internal carotids form the circle of Willis. (OpenStax A&P 2e, 20.5; StatPearls, Head and Neck: Internal Carotid Arteries, Thorax, Subclavian Arteries and Head and Neck: Carotid Arteries)

At the bifurcation sit the carotid sinus, which senses stretch in the artery wall, and the carotid body, which senses low oxygen, high carbon dioxide and low pH. (StatPearls, Head and Neck: Carotid Arteries)

The carotid artery in the neck is one of the usual places to feel a pulse, and in adult resuscitation it is the preferred site. (OpenStax A&P 2e, 20.2; StatPearls, Peripheral Pulse)

What runs beside the common carotid artery?

The internal jugular vein runs down beside it, inside the carotid sheath and just lateral to the artery. (OpenStax A&P 2e, 20.5; StatPearls, Head and Neck: Internal Jugular Vein and Head and Neck, Anterior: Common Carotid Arteries)

In the sheath the vagus nerve lies between the artery and the vein, a little behind them. (StatPearls, Head and Neck: Internal Jugular Vein)

How do the common carotid arteries vary?

The right common carotid sometimes arises straight from the aorta, and more rarely from the right subclavian artery. (StatPearls, Head and Neck, Anterior: Common Carotid Arteries)

Where the sources differ

OpenStax classes each branch of the aortic arch, the left common carotid among them, as an elastic artery. StatPearls (Common Carotid Arteries) calls the common carotids large muscular arteries. (OpenStax A&P 2e, 20.5; StatPearls, Head and Neck, Anterior: Common Carotid Arteries)

The two StatPearls articles differ on the usual level of the bifurcation. StatPearls (Carotid Arteries) puts it at the fourth or fifth cervical vertebra. StatPearls (Common Carotid Arteries) names C4 as the commonest site and says it can sit a little higher or lower. (StatPearls, Head and Neck: Carotid Arteries and Head and Neck, Anterior: Common Carotid Arteries)