Learning Objective: By the end of this session, the learner will be able to describe the anatomy, branches, and clinical relevance of the arterial supply to the head and neck, including the carotid and vertebral systems.
The head and neck receive most of their blood supply from the carotid arteries and the vertebral arteries, with the carotid system supplying the majority of both superficial and deep structures.
Carotid Arteries
Origin
- Right common carotid artery: arises from the brachiocephalic trunk near the right sternoclavicular joint.
- Left common carotid artery: arises directly from the arch of the aorta.
Both ascend the neck lateral to the trachea and esophagus and do not give off branches in the neck.
Bifurcation
- At the level of C4 (upper thyroid cartilage), each common carotid divides into:
- External carotid artery (ECA)
- Internal carotid artery (ICA)
- This occurs in the carotid triangle.
Carotid Sinus and Body
- Carotid sinus: dilation at the bifurcation containing baroreceptors; detects blood pressure.
- Innervation: glossopharyngeal nerve (CN IX).
- Carotid body: peripheral chemoreceptors sensing oxygen content.
Clinical Relevance: Carotid Sinus Hypersensitivity
Hypersensitive baroreceptors can cause bradycardia, hypotension, and syncope with minimal external pressure. Carotid palpation should be avoided in such patients.
External Carotid Artery (ECA)
The ECA supplies structures external to the cranium. It passes posterior to the mandibular neck, anterior to the ear, and terminates in the parotid gland as:
- Superficial temporal artery
- Maxillary artery
Main Branches (6)
- Superior thyroid artery
- Lingual artery
- Facial artery
- Ascending pharyngeal artery
- Occipital artery
- Posterior auricular artery
Facial, maxillary, and superficial temporal are the major clinically important branches.
Clinical Relevance: Scalp Blood Supply
The scalp bleeds heavily due to:
- Tightly bound arteries to connective tissue → cannot constrict
- Numerous arterial anastomoses
- Tension on deep lacerations from frontalis and occipitalis
The skull itself is supplied by the middle meningeal artery, so avascular necrosis does not occur.
Clinical Relevance: Extradural (Epidural) Haematoma
- The middle meningeal artery (MMA), a branch of the maxillary artery, supplies the skull and dura.
- Pterion fractures may tear the MMA → epidural hematoma.
- Symptoms: headache, seizures, vomiting, limb weakness, bradycardia.
- Treatment may require burr hole drainage.
Internal Carotid Artery (ICA)
The ICA gives no branches in the neck, entering the skull through the carotid canal.
Major supply targets include:
- Brain and brainstem
- Eyes
- Forehead
Clinical Relevance: Carotid Atherosclerosis
The carotid sinus region is prone to atheroma due to turbulent flow.
ICA stenosis causes neurological symptoms: dizziness, weakness, and headache.
Severe blockage → stroke.
Diagnosis: carotid Doppler.
Treatment: carotid endarterectomy.
