The carotid arteries represent the primary vascular pathway delivering oxygenated blood to the tissues of the head and neck. The system begins with the common carotid artery, which separates into two major divisions: the Internal Carotid Artery and the External Carotid Artery (ECA). The ECA is responsible for supplying the vast majority of structures located outside of the cranial cavity, including the face, neck, and scalp.
Anatomical Division of the Carotid System
The common carotid artery ascends the neck without branching until it reaches the superior border of the thyroid cartilage, approximately the fourth cervical vertebra (C4). Here, the vessel undergoes bifurcation, splitting into the internal and external carotid arteries. This anatomical division establishes the boundary for blood supply to the head and neck.
The Internal Carotid Artery (ICA) travels upward, entering the base of the skull to supply the brain and orbital structures, such as the eye. The External Carotid Artery (ECA) remains outside the cranial vault to nourish surrounding tissues. The ECA is generally smaller than the ICA at the point of bifurcation and provides eight major branches to the superficial and deep structures of the head and neck.
Supply to the Face and Scalp
The External Carotid Artery terminates within the parotid gland, dividing into its two final branches, the Superficial Temporal Artery and the Maxillary Artery. These two final branches are major contributors to the face and scalp supply. The Facial Artery, an anterior ECA branch, supplies the anterior face, including the lips, cheeks, and the side of the nose. It terminates as the Angular Artery near the medial corner of the eye.
The Superficial Temporal Artery ascends anterior to the ear, supplying the skin and muscles of the temporal region and parts of the lateral scalp. Its pulse is often easily felt due to its superficial position near the temporal bone. The Maxillary Artery, the largest terminal branch, travels deep into the face to supply structures that require significant blood flow for movement and sensation. This artery nourishes the muscles used for chewing, the teeth and gums, and the mucous membranes lining the nasal cavity and sinuses.
Middle Meningeal Artery
The Middle Meningeal Artery, a branch of the Maxillary Artery, ascends to supply the protective coverings of the brain, known as the dura mater, and the bones of the skull. This vessel is notable because it is one of the few ECA branches that crosses into the cranial cavity. Its path demonstrates how the ECA system supports the external layers of the head, including the skull and its immediate lining.
The coordinated supply from the Facial, Superficial Temporal, and Maxillary arteries ensures comprehensive blood flow to the musculature and skin of the entire anterior and lateral face.
Supply to the Tongue and Deep Neck Structures
The External Carotid Artery gives rise to several crucial branches that supply the deep neck and the oral cavity. The Superior Thyroid Artery is typically the first branch, descending to supply the upper pole of the thyroid gland. This artery also provides blood flow to the infrahyoid muscles and the upper part of the larynx itself. The consistent delivery of oxygenated blood is necessary for the metabolic activity of the thyroid gland.
The Lingual Artery arises anteriorly to supply the tongue and the floor of the mouth. It travels deep beneath the hyoid bone, supplying the intrinsic and extrinsic muscles of the tongue. This supply supports the movements involved in speech, swallowing, and taste sensation. The artery also provides circulation to the salivary glands and mucous membranes under the tongue.
Supply to the Pharynx and Meninges
The ECA supplies the deep and posterior regions of the head and neck through its final set of branches. The Ascending Pharyngeal Artery is the only branch that consistently arises from the medial side of the external carotid artery. It ascends along the side wall of the pharynx, supplying the pharyngeal constrictor muscles and the soft palate. This vessel also sends small branches that pierce the base of the skull to supply the meninges, the protective layers covering the brain and spinal cord.
The Occipital Artery emerges from the posterior side of the ECA, supplying the muscles in the back of the neck and the posterior region of the scalp. This vessel nourishes the large muscles responsible for head movement and posture. The Posterior Auricular Artery arises near the parotid gland to supply the structures behind the ear and the adjacent scalp. These posterior and deep branches complete the ECA’s comprehensive coverage.