Common carotid artery

The common carotid arteries (also known as carotid arteries or carotids, Latin: (sg.) arteria carotis communis) are large blood vessels that provide arterial blood supply to the head and neck. The right and left carotids arise asymmetrically but follow similar courses. On the left side, the common carotid artery branches off directly from the arch of the aorta, while on the right side the carotid arises from the brachiocephalic trunk as it travels posteriorly to the sternoclavicular joint. At the level of C3-C4 junction, the common carotid artery bifurcates into two branches: the internal and external carotid arteries, which further divides into branches supplying the head and neck region.


Anatomy of carotids

The left common carotid artery is longer than the right having cervical and thoracic parts, whereas the right common carotid artery has only a cervical part. After separating from the aortic arch, the left common carotid artery ascends through the superior mediastinum up to the level of the left sternoclavicular joint.

The cervical part of the common carotid artery is symmetrical on both sides. The carotid ascends from behind the sternoclavicular joint up to the level of the upper border of the thyroid cartilage of the larynx, where each carotid bifurcates into the internal and external carotid arteries.

Each common carotid artery lies within the carotid sheath of the deep cervical fascia. The carotid sheath contains the following structures: common carotid artery (medial), internal jugular vein (lateral), vagus nerve (posterior), ansa cervicalis (anterior), and the deep cervical lymph nodes.


Carotid body

Near its bifurcation, the common carotid artery has a carotid body - a cluster of chemoreceptors that are sensitive to the chemical composition of the arterial blood flowing through the artery. Hypoxia (low oxygen levels in the blood), hypercapnia (elevated carbon dioxide levels in the blood), or increased hydrogen ion concentration stimulates the carotid body to elicit a reflex. This reflex increases the rate and volume of ventilation via connections with the respiratory centers in the brainstem. Individuals with chronic hypoxia or who live at high altitudes may have enlarged carotid bodies.


Carotid pulse

The pulse of the common carotid artery can easily be felt by touch (palpated) in the neck beneath the anterior border of the sternocleidomastoid muscle. The carotid pulse is best palpated by compressing three fingertips against the prominent transverse process of the sixth cervical vertebra.