External Carotid Artery
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Direct answer
Eight branches spring from the external carotid artery between its origin at the bifurcation of the common carotid — at the upper border of the thyroid cartilage, about C4 — and its termination behind the neck of the mandible, where it divides into the maxillary and superficial temporal arteries: the superior thyroid, ascending pharyngeal, lingual, facial, occipital, posterior auricular, and the two terminal branches. It supplies the face, scalp, jaws, oral cavity, pharynx and neck, begins anteromedial to the internal carotid and spirals to become lateral, and is the artery of epistaxis control and head and neck tumour embolisation. The order of its branches, front and back alternating, is a mandatory viva recitation.
What you must remember
- Anterior branches: superior thyroid (with the superior laryngeal branch), lingual and facial; posterior branches: occipital and posterior auricular; medial: ascending pharyngeal; terminal: maxillary and superficial temporal.
- The lingual artery arises deep to the hyoglossus, and the hypoglossal nerve loops over its origin — the classic pair of relations for tongue surgery.
- It lies first anteromedial, then lateral, to the internal carotid; the internal carotid gives no branches in the neck, the external gives eight.
- The superior thyroid artery accompanies the external laryngeal nerve, which may be injured when the artery is ligated far from the gland during thyroidectomy.
- The artery is crossed by the hypoglossal nerve, the posterior belly of digastric and the facial vein's tributaries within the parotid region.
- The facial artery hooks over the submandibular gland, crosses the mandible at the antegonial notch, and its labial branches anastomose freely across the midline — hence facial lacerations bleed vigorously but heal well.
- Collaterals between external carotid branches and the ophthalmic artery (angular anastomoses) connect extracranial and intracranial circulation.
A typical exam case: severe epistaxis refractory to packing
A forty-year-old with uncontrolled posterior epistaxis despite balloon tamponade, hypertension and a swelling cheek is the scenario that puts this artery centre stage. Follow the pathway a head and neck surgeon takes. Persistent posterior bleeding arises from the sphenopalatine artery territory, itself a branch of the maxillary artery, the larger terminal branch of the external carotid. Step one per current practice is endoscopic sphenopalatine artery cauterisation or clipping at the sphenopalatine foramen; if bleeding continues from multiple sites, the next rung is endovascular embolisation of the ipsilateral internal maxillary artery, and selective external carotid artery ligation remains a surgical fallback.
Now the anatomy of ligation. The common carotid bifurcation is marked at the upper border of the thyroid cartilage; the external carotid is identified in the carotid triangle by its branches — the internal carotid has none in the neck — and the superior thyroid artery's origin is the guard against mistaking one vessel for the other. Ligation works because collateral flow across the midline through the facial and superficial temporal arcades is incomplete on the side of ligation; but the angular–ophthalmic anastomosis means embolic material must be delivered distal to dangerous connections, and the ascending pharyngeal artery's middle meningeal connections caution the interventionalist against non-selective injection, since skin necrosis and neurological deficit are the recognised misadventures.
Where students slip
The order of branches is the slip zone: candidates reverse the lingual and facial or promote the ascending pharyngeal to a posterior vessel. The mnemonic in universal Indian use — "Some Anatomists Like Freaking Out Poor Medical Students" — encodes superior thyroid, ascending pharyngeal, lingual, facial, occipital, posterior auricular, maxillary and superficial temporal, and reciting it with each branch's territory is the expected standard. The second error is placing the bifurcation "at the angle of the mandible"; the landmark is the upper border of the thyroid cartilage at C4, with the angle of the mandible roughly opposite C2–C3 and the cricoid at C6. Third, students forget that the occipital artery's groove marks the medial part of the temporal bone's mastoid notch region and that the artery anastomoses with the deep cervical branch of the costocervical trunk — an anastomosis that can defeat simple ligation.
Frequently asked questions
Where does the external carotid artery begin and end?
It begins at the bifurcation of the common carotid at the upper border of the thyroid cartilage (about C4) and ends behind the neck of the mandible by dividing into the maxillary and superficial temporal arteries.
Which branches arise from its anterior aspect?
The superior thyroid, lingual and facial arteries.
Which nerve loops around the origin of the occipital artery?
The hypoglossal nerve, which then runs forward on the external carotid and lingual artery towards the tongue.
How is the external carotid distinguished from the internal carotid in the neck?
By its branches — the internal carotid has none in the neck — and by its position, anteromedial first, becoming lateral to the internal carotid.
What connects the external carotid territory with the intracranial circulation?
Anastomoses between the angular branch of the facial artery and branches of the ophthalmic artery, plus meningeal twigs of the ascending pharyngeal and maxillary arteries.