Left common carotid artery

At a glance

English

Left common carotid artery

Latin (TA2)

Carotis communis sinistra

System

Artery

Region

Neck

Side

Single, on the midline

About the left common carotid artery

The left common carotid artery carries blood to the left side of the head and neck. Unlike its partner on the right, which springs from the brachiocephalic trunk low in the neck, it arises straight from the aortic arch, between the brachiocephalic trunk and the left subclavian artery. It therefore has two parts: a thoracic part in the superior mediastinum and a cervical part in the neck, which mirrors the right artery closely.

In the chest it ascends to the back of the left sternoclavicular joint. In front lie the manubrium, separated from it by sternohyoid and sternothyroid, the anterior margins of the left lung and its pleura, the thymic remnant and the left brachiocephalic vein. Behind it are the trachea and oesophagus, with the thoracic duct and the left recurrent laryngeal nerve, with the left subclavian artery behind and to its left. The brachiocephalic trunk lies to its right below, the trachea higher up, and the left phrenic and vagus nerves, pleura and lung on its left side.

In the neck it runs up within the carotid sheath alongside the internal jugular vein, which is lateral, and the vagus nerve, which lies behind and between them. Low down it is deep, covered by sternocleidomastoid and the infrahyoid muscles, and here the left internal jugular vein often overlaps it. Higher up, in the carotid triangle, it becomes superficial under the front edge of sternocleidomastoid. Behind it are longus colli and longus capitis with the sympathetic trunk in front of them; medially lie the trachea, oesophagus, thyroid gland and recurrent laryngeal nerve, and later the larynx and pharynx. The superior root of the ansa cervicalis runs down on the front of the sheath. Level with the top of the thyroid cartilage, roughly C4, it divides into internal and external carotid arteries, with the carotid sinus and carotid body at the fork. It normally gives no other branches.

The carotid pulse is felt at the front edge of sternocleidomastoid level with the top of the thyroid cartilage and is used when peripheral pulses are lost. Atherosclerosis at the bifurcation narrows the vessel and is a major cause of stroke, treated by endarterectomy or stenting. The origin varies; most often the left artery shares a stem with the brachiocephalic trunk.

Course and supply

Arises from

Arises directly from the upper border of the aortic arch, between the brachiocephalic trunk and the left subclavian artery.

Ends in

Ends level with the top of the thyroid cartilage, about the level of C4, by dividing into the left internal and external carotid arteries.

Supplies

Carries the arterial supply for the left side of the head and neck: the left half of the brain and eye through the internal carotid, and the face, scalp and neck through the external carotid.