Chief artery of supply to structures in front of neck and face. One of two terminal branches of common carotid artery.

Origin and Termination

• Begins in carotid triangle at upper border of thyroid cartilage (opposite disc between C3–C4) where CCA bifurcates
• Runs upward, slightly backward + laterally
• Terminates behind neck of mandible → divides into 2 terminal branches: maxillary artery + superficial temporal artery

Course and Relations

• Anteromedial to ICA in lower part; anterolateral to ICA in upper part
• In carotid triangle: comparatively superficial, under anterior border of SCM
• Above carotid triangle: deep within parotid gland; within gland, related superficially to retromandibular vein + facial nerve; deep = ICA + structures between ECA/ICA (styloglossus, stylopharyngeus, CN IX, pharyngeal branch of vagus, styloid process, superior laryngeal nerve, superior cervical sympathetic ganglion)
• Stylomandibular ligament pierced by ECA

Carotid Sinus and Body

• Carotid sinus — dilatation at CCA bifurcation; baroreceptor; innervated by CN IX + sympathetic
• Carotid body — small chemoreceptor behind bifurcation; responds to O2, CO2, pH; supplied mainly by CN IX (also vagus + sympathetic)

8 Branches (Grouped by Direction)

1. Superior Thyroid Artery

• Just below greater cornu of hyoid; runs downward + forward; accompanied by external laryngeal nerve (EBSLN) (running medial to it) → upper pole of lateral thyroid lobe
• Gives: superior laryngeal artery (pierces thyrohyoid membrane with internal laryngeal nerve), sternocleidomastoid branch, cricothyroid branch
• Surgical significance: Artery + EBSLN close together proximally but diverge near gland → ligate at upper pole capsule to protect EBSLN

2. Lingual Artery

• Arises opposite tip of greater cornu of hyoid; tortuous; 3 parts (divided by hyoglossus):
  • 1st part (carotid triangle): upward loop crossed by hypoglossal nerve; permits hyoid movement; ligated here before tongue/tonsil branches
  • 2nd part (deep to hyoglossus): along upper border of hyoid; superficial to middle constrictor
  • 3rd part (arteria profunda linguae): runs upward along anterior border of hyoglossus → horizontal forward on undersurface of tongue, between genioglossus (medial) + inferior longitudinal (lateral); accompanied by lingual nerve

3. Facial Artery

• Just above tip of greater cornu of hyoid
• Cervical part: runs up on superior constrictor; deep to posterior belly of digastric + stylohyoid; grooves posterior border of submandibular gland; S-shaped course (loops down over gland, then up over base of mandible)
• Facial part: enters face at anteroinferior angle of masseter → runs up close to angle of mouth + side of nose → medial angle of eye
• Cervical branches: ascending palatine (between styloglossus + stylopharyngeus → tonsil + root of tongue), tonsillar, submental (large; accompanies mylohyoid nerve; supplies submental triangle + sublingual gland), glandular branches

4. Occipital Artery

• Posterior aspect of ECA; crossed at origin by hypoglossal nerve
• In carotid triangle: gives sternocleidomastoid branches (upper accompanies accessory nerve)
• Continues into scalp

5. Posterior Auricular Artery

• Just above posterior belly of digastric; deep to parotid, superficial to styloid process; crosses mastoid base; ascends behind auricle
• Stylomastoid branch enters stylomastoid foramen → supplies middle ear, mastoid, semicircular canals, facial nerve
• Cut during mastoid operations

6. Ascending Pharyngeal Artery

• Small branch from medial side of ECA near its origin; runs vertically upward between pharyngeal side wall + medial wall of middle ear/auditory tube; sends meningeal branches through foramen lacerum

7. Superficial Temporal Artery (Terminal)

• Palpable at preauricular point
• Gives transverse facial artery + middle temporal artery

8. Maxillary Artery (Terminal — Larger)

• Supplies deep structures of face (infratemporal fossa + pterygopalatine fossa)

Applied Anatomy

• ECA vs ICA in neck: ECA gives off branches in neck (ICA gives none); ECA anteromedial → anterolateral to ICA; structures between them (styloglossus, stylopharyngeus, CN IX, pharyngeal vagus, styloid process) = surgical landmark for distinguishing vessels
• Superior thyroid + EBSLN: ligate artery close to gland (where they’ve diverged) → avoids nerve injury
• Tight neckties: may compress both ICAs → reduced cerebral blood flow

The external carotid artery (ECA) is one of the two terminal branches of the common carotid artery and is the chief artery of supply to structures in the front of the neck and the face.

Origin and Termination

The ECA begins in the carotid triangle, at the level of the upper border of the thyroid cartilage, opposite the disc between the third and fourth cervical vertebrae — where the common carotid artery bifurcates into the external and internal carotid arteries. The ECA runs upward, slightly backward and laterally, and terminates behind the neck of the mandible by dividing into its two terminal branches: the maxillary artery and the superficial temporal artery.

Course and Relations

• The ECA has a slightly curved course: it lies anteromedial to the internal carotid artery (ICA) in its lower part, and anterolateral to the ICA in its upper part.
• In the carotid triangle, the ECA is comparatively superficial, lying under cover of the anterior border of the sternocleidomastoid.
• Above the carotid triangle, the ECA lies deep within the substance of the parotid gland. Within the gland, it is related superficially to the retromandibular vein and the facial nerve.
• Deep to the ECA (above the carotid triangle) lie: the internal carotid artery; structures passing between the external and internal carotid arteries (styloglossus, stylopharyngeus, glossopharyngeal nerve, pharyngeal branch of the vagus, styloid process); and, deeper still, the superior laryngeal nerve and the superior cervical sympathetic ganglion.
• The stylomandibular ligament (a thickened part of the parotid fascia separating the parotid gland from the submandibular gland) is pierced by the external carotid artery.

Carotid Sinus and Carotid Body

At the origin of the ECA/ICA, the common carotid artery shows a dilatation — the carotid sinus — which acts as a baroreceptor, richly innervated by the glossopharyngeal and sympathetic nerves. The carotid body, a small chemoreceptor structure behind the bifurcation, responds to changes in oxygen, carbon dioxide, and pH, and is supplied mainly by the glossopharyngeal nerve (also vagus and sympathetic).

Branches of the External Carotid Artery

The ECA gives off eight branches, grouped by direction as follows:

1. Superior Thyroid Artery

Arises just below the level of the greater cornu of the hyoid bone. Runs downward and forward, parallel and just superficial to the external laryngeal nerve (supplying cricothyroid), passing deep to the three long infrahyoid muscles to reach the upper pole of the lateral lobe of the thyroid gland. Gives off the superior laryngeal artery, which pierces the thyrohyoid membrane along with the internal laryngeal nerve, plus sternocleidomastoid and cricothyroid branches. The artery and external laryngeal nerve are close together higher up but diverge near the gland — the artery is therefore ligated as close to the gland as possible during thyroid surgery, to avoid injuring the nerve.

2. Lingual Artery

Arises opposite the tip of the greater cornu of the hyoid bone; tortuous in course, divided into three (sometimes described as four) parts by the hyoglossus muscle:

• First part — lies in the carotid triangle, forms a characteristic upward loop crossed by the hypoglossal nerve (permits free hyoid bone movement).
• Second part — deep to hyoglossus, along the upper border of the hyoid bone, superficial to the middle constrictor.
• Third part (arteria profunda linguae / deep lingual artery) — runs upward along the anterior border of hyoglossus, then horizontally forward on the undersurface of the tongue, between genioglossus (medially) and inferior longitudinal muscle of tongue (laterally); accompanied by the lingual nerve.

During surgical removal of the tongue, the first part of the lingual artery is ligated before it gives any branch to the tongue or tonsil.

3. Facial Artery

Arises just above the tip of the greater cornu of the hyoid bone.

• Cervical part — runs upward on the superior constrictor of the pharynx, deep to the posterior belly of digastric and stylohyoid, grooves the posterior border of the submandibular salivary gland, then makes an S-shaped course (two loops) — first winding down over the submandibular gland, then up over the base of the mandible.
• Facial part — enters the face at the anteroinferior angle of the masseter, runs upward close to the angle of the mouth and side of the nose to the medial angle of the eye.

Cervical part branches: ascending palatine (supplies tonsil and root of tongue, passing between styloglossus and stylopharyngeus), tonsillar, submental (large, accompanies the mylohyoid nerve, supplies the submental triangle and sublingual gland), and glandular branches to the submandibular gland and lymph nodes.

4. Occipital Artery

Arises from the posterior aspect of the ECA, crossed at its origin by the hypoglossal nerve. In the carotid triangle it gives two sternocleidomastoid branches (the upper accompanies the accessory nerve). Continues into the scalp.

5. Posterior Auricular Artery

Arises from the posterior aspect of the ECA just above the posterior belly of digastric. Runs upward and backward deep to the parotid gland but superficial to the styloid process, crosses the base of the mastoid process, and ascends behind the auricle — supplying the back of the auricle, skin over the mastoid process and back of the scalp. Cut during mastoid operations. Its stylomastoid branch enters the stylomastoid foramen to supply the middle ear, mastoid antrum and air cells, semicircular canals, and the facial nerve.

6. Ascending Pharyngeal Artery

A small branch arising from the medial side of the ECA, close to its origin. Runs vertically upward between the side wall of the pharynx and the medial wall of the middle ear/auditory tube, sending meningeal branches into the cranial cavity through the foramen lacerum.

7. Superficial Temporal Artery (Terminal Branch)

One of the two terminal branches; can be palpated at the preauricular point. Gives off the transverse facial artery and the middle temporal artery (runs on the temporal fossa deep to temporalis).

8. Maxillary Artery (Terminal Branch)

The larger terminal branch; supplies deep structures of the face (described in detail separately in the context of the infratemporal fossa and pterygopalatine fossa).

Mnemonic for Branches (Directional Grouping)

• Anterior: Superior thyroid, Lingual, Facial
• Posterior: Occipital, Posterior auricular
• Medial: Ascending pharyngeal
• Terminal: Superficial temporal, Maxillary

(Memory aid — only medial branch: Ascending pharyngeal.)

Ansa Cervicalis (Related Structure)

A thin nerve loop embedded in the anterior wall of the carotid sheath over the lower part of the larynx, supplying the infrahyoid muscles.

• Superior root — continuation of the descending branch of the hypoglossal nerve (fibres from C1), descends over the internal and common carotid arteries.
• Inferior root (descending cervical nerve) — derived from C2 and C3, winds round the internal jugular vein, continues anteroinferiorly to join the superior root in front of the common carotid artery.
• Distribution: Superior root supplies the superior belly of omohyoid; the ansa cervicalis loop supplies sternohyoid, sternothyroid, and the inferior belly of omohyoid. (Thyrohyoid and geniohyoid are supplied separately by C1 fibres travelling via the hypoglossal nerve.)

Clinical Correlation

Pulse Palpation: The common carotid artery can be palpated at the anterior border of sternocleidomastoid — a site sometimes used by an anaesthetist to monitor pulse during surgery. The superficial temporal and facial arteries are also palpable in the head and neck.

Ligation Safety: The relationship between the superior thyroid artery and the external laryngeal nerve is critical during thyroid surgery — ligating the artery close to the thyroid gland (where the artery and nerve have diverged) avoids nerve injury.

Tight Neckties: A tightly tied necktie may compress both internal carotid arteries (which supply the brain), potentially reducing cerebral blood flow.

ECA vs ICA Distinguishing Features: In the neck, the ECA gives off branches (the ICA gives none in the neck), lies anteromedial then anterolateral to the ICA, and is more superficial in the carotid triangle. The structures passing between the ECA and ICA (styloglossus, stylopharyngeus, glossopharyngeal nerve, pharyngeal branch of vagus, styloid process) are a useful landmark for distinguishing the two vessels surgically.

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