In the head and neck, the common carotid arteries play a central role in blood supply. These major vessels ascend through the neck, providing blood flow to nourish the brain and other structures. The common carotid arteries divide into two main branches: the internal carotid artery and the external carotid artery. While the internal carotid artery primarily supplies the brain and eyes, the external carotid artery is responsible for blood supply to the external structures of the head and face.
The External Carotid Artery’s Role
The external carotid artery originates from the common carotid artery, typically at the level of the thyroid cartilage in the neck. It ascends through the neck, diminishing in size as it gives off several branches. Its function is to supply oxygenated blood to the face, scalp, neck, and specific areas within the oral cavity and pharynx. Unlike the internal carotid artery, it supplies areas of the head and neck external to the cranium, distinguishing its role from the internal carotid’s intracranial supply. The external carotid artery terminates near the ear, within the parotid gland.
Branches to the Front of the Head and Neck
Several branches of the external carotid artery supply the anterior regions of the head and neck. The superior thyroid artery is typically the first branch to emerge, supplying the thyroid gland and parts of the larynx. The lingual artery branches off to supply the tongue and the floor of the mouth, which are vital for speech and digestion. The facial artery then emerges, providing blood to a broad area including the face, lips, and nose. Its winding path allows it to reach various facial muscles and skin.
Branches to the Back of the Head and Neck
The external carotid artery also gives rise to branches that supply the posterior and medial regions of the head and neck. The ascending pharyngeal artery is a medial branch, supplying structures such as the pharynx, tonsils, soft palate, and parts of the ear, often arising from the deep aspect of the external carotid. The occipital artery typically branches from the posterior aspect, providing blood to the back of the scalp, the sternocleidomastoid muscle, and deep muscles of the back. Another posterior branch is the posterior auricular artery, which supplies the ear and the scalp behind the ear. This artery ascends between the parotid gland and the styloid process.
The Major Terminal Branches
The external carotid artery concludes its course by dividing into two major terminal branches, typically within the parotid gland. The superficial temporal artery is one of these terminal branches, ascending superficially alongside the auriculotemporal nerve, and primarily supplies parts of the scalp, the side of the face, and the parotid gland. The maxillary artery is the other significant terminal branch, with extensive subdivisions. This artery is crucial for supplying deep structures of the face, including the nasal cavity, teeth, and parts of the dura mater. It divides into three parts based on its relationship to the lateral pterygoid muscle, each part giving off multiple branches.
Why Understanding These Branches Matters
Knowledge of the external carotid artery’s branches is important in medical and surgical contexts. In head and neck surgical procedures, understanding the precise location of these arteries is crucial to manage bleeding risks. Procedures like thyroid surgery or maxillofacial surgery often require specific arteries, such as the superior thyroid or facial artery, to be identified and potentially managed. These branches also serve as accessible pulse points, with the superficial temporal artery being a common site for palpation. This anatomical understanding aids in diagnosing conditions affecting blood flow to the face and neck, and helps clinicians trace the spread of infections or tumors, aiding precise patient care.