Common carotid artery
The common carotid arteries (also known as carotid arteries, carotids, latin: (sg.) arteria carotis communis) 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 it arises from the brachiocephalic artery as it goes posteriorly to the sternoclavicular joint. At the level of C3-C4 junction the common carotid artery bifurcates into two arteries: the internal and external carotid arteries, supplying the head and neck region.
The left common carotid artery is longer than the right having a cervical and a thoracic part, whereas the right common 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 common carotid artery ascends from behind the sternoclavicular joint up to the level of the upper border of the thyroid cartilage of the larynx, where it 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 common carotid artery (medial), the internal jugular vein (lateral), the vagus nerve (posterior), the cervical ansa (anterior), and the deep cervical lymph nodes.
Near its bifurcation the common carotid artery has a carotid body that is a cluster of chemoreceptors which are sensitive to chemical composition of the arterial blood. Hypoxia, hypercapnia or increased hydrogen ion concentration stimulates the carotid body to elicit a reflex increasing the rate and volume of ventilation via connections with the brainstem respiratory centres. Individuals with chronic hypoxia or who live at high altitude may have enlarged carotid bodies.
The common carotid artery pulse can easily be felt in the neck beneath the anterior border of sternocleidomastoid muscle by compressing the fingertips against the prominent transverse process of the sixth cervical vertebra.
Common pathologies that affect the common carotid artery are: atherosclerosis, carotid artery embolism, carotid artery aneurysm.