Common carotid aa.

The left and right common carotid arteries supply the head and neck with oxygenated blood. They divide in the neck to form the external and internal carotid arteries.

The left and right common carotid arteries follow the same course with the exception of their origin. The right common carotid originates in the neck from the brachiocephalic trunk. The left arises from the aortic arch in the thoracic region. The bifurcation into the external and internal carotid arteries occurs at the upper border of the thyroid cartilage at around the level of the fourth cervical vertebra (C4.)

The left common carotid artery can be thought of as having two parts: a thoracic (chest) part and a cervical (neck) part. The right common carotid originates in or close to the neck, so its thoracic portion is very short. There are studies in the bioengineering literature that have looked into characterizing the geometric structure of the common carotid artery from both qualitative and mathematical (quantitative) standpoints.