Common carotid artery

The common carotid artery is a paired structure that supplies blood to the head and neck. 

Summary

• origin:
  • left: branch of the aortic arch
  • right: branch of the brachiocephalic trunk
• course: posterior to sternoclavicular joint, lateral to thyroid and trachea
• supply: head and neck
• main branches: none (usually)
• termination: at the carotid bifurcation to form the external and internal carotid arteries
• key relationships: internal jugular vein and vagus nerve

Gross anatomy

Origin and course

Although the left and right common carotid arteries follow the same course through the neck, their origin differs.

On the left, the common carotid arises directly from the aortic arch whereas, on the right, the origin is from the brachiocephaic trunk. The left common carotid artery can be thought of as having two distinct parts: thoracic and cervical. Since the right common carotid arises cranially, it only really has a cervical portion.

In the thoracic section, the left common carotid travels upwards through the superior mediastinum to the level of the left sternoclavicular joint where it is continuous with the cervical portion.

The cervical section of both common carotids follows a similar course. Each vessel passes obliquely upwards from behind the sternoclavicular joint to the level of the upper border of the thyroid cartilage. In the lower neck, the two common carotid arteries are separated from each other by the trachea. However, as the carotids rise in the neck, they diverge come to be separated by the thyroid gland, the larynx and pharynx.

Each common carotid is contained within the carotid sheath which is derived from all 3 layers of the deep cervical fascia. In addition to containing the common carotid artery, the sheath also comprises the internal jugular vein and vagus nerve: the vein lies lateral to the artery, with the nerve in between the two. At the level of the fourth cervical vertebra, the vessel bifurcates into the external and internal carotids.