External carotid artery (ECA)

Begins at the common carotid artery bifurcation at the level of C4-3, it ascends anteriorly and medially to the ICA bordered medially by the hyoid bone, the walls of the pharynx, the superior larygeal nerve and the parotid gland. It enters the parotid gland and branches off into its terminal branches, the superficial temporal artery and the maxillary artery.


Branches:
  1. Superior thyroid artery
    • Arises from the anterior aspect of the ECA, within the carotid triangle, just below the level of the greater cornu of the hyoid bone and reaches the superior aspect of the thyroid gland
    • Gives off infrahyoid and sternocleidomastoid branches to adjacent neck muscles, as well as superior laryngeal artery and cricothyroid artery to the larynx

  1. Ascending pharyngeal artery
    • Arises from the posterior medial aspect of the ECA within the carotid triangle, usually near the carotid bifurcation. Courses outside the carotid sheath, medially to it, between the ICA and the lateral pharyngeal wall. Has two distinct divisions:
      1. The pharyngeal division is more anterior and supplies the posterior and lateral walls of the nasopharynx, oropharynx and hypopharynx. It reaches the skull base and may form anastomoses with intracranial branches through the foramen lacerum
      2. The neuromeningeal trunk is more posterior. Its more proximal cervical portion collateralizes with the vertebral artery via spinal and muscular branches. More distally it divides into:
        1. Hypoglossal division:
          • Enters the skull through the hypoglossal canal
          • Supplies the hypoglossal nerve and adjacent dura
          • It forms anastomotic networks with the middle meningeal artery and the meningohypophyseal trunk
        2. Jugular division
          • Enters the skull through the jugular foramen and runs posterolaterally
          • Supplies the glossopharyngeal, vagus and accessory nerves. Supplies the dura around the jugular foramen as well as the posterior cranial fossa with branches running along the sigmoid sinus

  1. Lingual artery
    • Arises within the carotid triangle, either from the ECA proximal to the facial atery or from a common faciolingual trunk
    • Branches:
      • Suprahyoid artery: along the upper border of the hyoid bone supplying adjacent muscles
      • Sublingual artery: runs between the genioglossus and mylohyoideus muscles to supply the sublingual gland and gives off small branches to adjacent muscles, mucous membranes of the mouth and gums. May anastomose with the contralateral artery medially behind the alveolar process of the mandible as well as with the submental branch of the facial artery through the mylohyoideus muscle
      • Dorsal lingual arteries: arise beneath the hyoglossus, ascend to the posterior part of the dorsum of the tongue and supply the mucous membranes, glossopalatine arch, tonsils, soft palate and epiglottis
      • Deep lingual artery: terminal branch after the sublingual artery is given off. Travels under the ventral surface of the tongue laterally to the genioglossus muscle, accompanied by the lingual nerve. Supplies the intrinsic muscles of the tongue and the mucosa of the anterior 2/3 of the tongue

  1. Facial artery

    • Arises within the carotid triangle from the anterior aspect of ECA distal to the lingual artery or from a common faciolingual trunk.

    • The cervical segment ascends to the digastric and stylohyoid muscles, deep to the submandibular gland. Curves around the inferior border of the mandible.

    • Branches:

      1. Ascending palatine artery: ascends along the pharynx between the styloglossus and the stylopharyngeus muscles. Supplies soft palate, palatine tonsil and pharyngotympanic tube
      2. Tonsilar artery: penetrates the superior pharyngeal constrictor and supplies the palatine tonsil and surrounding pharyngeal wall. May sometimes arise from the ascending palatine artery
      3. Submandibular branches to the submandibular gland
      4. Submental artery: arises as the artery emerges beneath the submandibular gland, courses anteromedially along the mylohyoideus muscle beneath the digastricus. Supplies branches to the mylohyoid, anterior belly of digastricus, skin of the chin and lower lip. Anastomoses with submental branches from the inferior alveolar artery, mental artery and contralateral submental artery

    • The facial segment runs across the face superficial to the buccinator and facial muscles to the angle of the mouth and ascends along the side of the nose to reach the medial canthus.

    • Branches:

      1. Inferior labial artery: Courses beneath the triangularis and penetrates the orbicularis oris. Supplies the orbicularis oris muscle and the lower lip mucosa and glands
      2. Superior labial artery: Runs deep to the orbicularis oris and supplies the upper lip, parts of the nasal septum and ala of the nose
      3. Lateral nasal artery: runs along the lateral surface of the nose and supplies the ala and dorsum of the nose. Anastomoses with the contralateral artery as well as with the dorsal nasal branch of the ophthalmic artery and the infraorbital branch of the maxillary artery
      4. Angular artery: the terminal branch of the facial artery, ascends to the medial canthus and supplies branches to the lacrimal sac, the orbicularis oculi and nose. Anastomoses with the dorsal nasal branch of the ophthalmic artery

  1. Occipital artery
    • Arises from the posterior aspect of the ECA, usually opposite the to the origin of the facial artery. Runs posteriorly and superiorly deep to the posterior belly of the digastric muscle and the stylohyoid muscle and travels along the posterior border of the sternocleidomastoideus muscle, around the mastoid process and onto the posterior scalp.
    • Gives off:
      1. Auricular branch to the posterior part of the external ear and adjacent scalp. May give rise to a mastoid branch supplying the mastoid cells, diploe and part of dura, alternatively this branch may arise directly from the occipital artery
      2. Muscular branches to digastric, stylohyoid, splenius capitis, longus capitis and sternocleidomastoid muscles
      3. Meningeal branches: may enter the skull through the jugular foramen, the condylar canal or penetrate transosseously and supply the dura of the posterior cranial fossa
      4. Descending branch: descends along the posterior aspect of the neck and divides into superficial and deep portions: the superficial portion anastomoses with the transverse cervical artery, the deep portion anastomoses with the vertebral or deep cervical artery

  1. Posterior auricular artery
    • Arises from the ECA posterior to the external acoustic meatus, near the styloid process, superior to the digastric and stylohyoid muscles, distal to the origin of the occipital artery. Passes beneath the parotid gland and styloid process
    • Gives off:
      • Auricular branches supply the posterior and medial aspects of the external ear
      • Branches to the digastric muscle, stylohyoid muscle, sternocleidomastoid muscle, parotid gland and posterior scalp around the mastoid region
      • Stylomastoid artery: enters the stylomastoid foramen to provide arterial supply to the facial nerve, middle ear, mastoid cells and semicircular canals

  1. Maxillary artery

    • The largest of the two terminal branches of the ECA, arises typically behind the neck of the mandible, within or deep to the parotid gland

    • Passes anteriorly and medially through the infratemporal fossa, crossing either superficial or deep to the lateral pterygoid muscle

    • Continues into the pterygopalatine fossa via the pterygomaxillary fissure

    • Divided into mandibular, pterygoid, and pterygopalatine portions:

      1. The first (mandibular) portion courses posterior to lateral pterygoid muscle, passes horizontally and supplies mainly bony structures

        • Branches:
          1. Deep auricular artery: supplies the external acoustic meatus and outer tympanic membrane and temporomandibular joint
          2. Anterior tympanic artery: supplies the tympanic membrane and middle ear structures
          3. Middle meningeal artery
            • Enters the skull via foramen spinosum and gives off branches supplying the dura and calvaria, the trigeminal ganglion
            • A superficial petrosal branch enters the hiatus of the facial canal and supplies the facial nerve, anastomosing with the stylomastoid branch of the posterior auricular artery
            • A superior tympanic branch along the canal of the tensor tympani muscle supplies tensor tympani and the lining of the canal
            • Temporal branches passing through the greater wing of the sphenoid anastomose in the temporal fossa with deep temporal arteries
            • Forms extensive anastomoses with the anterior and posterior meningeal arteries the contralateral middle meningeal artery, the accessory meningeal artery, the meningohypophyseal trunk and inferolateral trunk from ICA, branches from the neuromeningeal division of the ascending pharyngeal artery, meningeal branches from the occipital artery and posterior auricular artery as well as the ophthalmic artery and its lacrimal branch
            • Rarely the ophthalmic artery may arise as a branch of the middle meningeal artery
          4. Accessory middle meningeal artery:
            • Enters the cranial cavity through foramen ovale and supplies parts of dura, the floor of the middle cranial cavity, part of the cavernous sinus and the trigeminal ganglion
            • May anastomose with the meningohypophyseal trunk, the inferolateral trunk, the middle meningeal artery and ascending palatine arteries
            • May sometimes arise from the middle meningeal artery
          5. Inferior alveolar artery: enters the mandibular foramen with the inferior alveolar nerve. Supplies mandibular teeth, the mandible, the lower lip and chin via its terminal branch, the mental artery

      2. The second (pterygoid) portion lies superficial or deep to the lateral pterygoid muscle and runs obliquely anteriorly and uppward along the ramus of the mandible and enters the pterygoid fossa. Gives off muscular branches:

        1. Deep temporal arteries (anterior and posterior): ascend deep to the temporalis muscle which they supply. May anastomose with the superficial temporal artery and branches from middle meningeal artery
        2. Pterygoid branches supply the medial and lateral pterygoid muscles
        3. Masseteric artery passes laterally through the mandibular notch to the deep surface of the masseter muscle which it supplies. May anastomose with the transverse facial artery and small masseteric branches from the facial artery
        4. Buccal artery supplies the buccinator muscle and the cheek

      3. The third (pterygopalatine) portion is the terminal portion of the maxillary artery, lies in the pterygopalatine fossa close to the pterygopalatine ganglion, and gives off branches to the deep face, orbit and skull base:

        1. Posterior superior alveolar artery enters posterior maxilla via foramina on the posterior wall of the maxillary sinus and supplies the molar and premolar teeth, maxillary sinus and adjacent bone and gingiva
        2. Infraorbital artery travels through the inferior orbital fissure, infraorbital groove, and infraorbital canal and exits through the infraorbital foramen to supply the lower eyelid, upper lip and lateral nose. Within the infraorbital canal it gives off the anterior and middle superior alveolar arteries to the anterior (incisor and canine) maxillary teeth, as well as orbital branches partly supplying the inferior rectus and oblique muscles
        3. Descending palatine artery descends through the greater palatine canal, dividing into the greater palatine artery supplying the hard palate and septum, and the lesser palatine artery supplying the soft palate and palatine tonsils
        4. Artery of the pterygoid canal (vidian artery) can arise from either the ICA or ECA or serve as an anastomosis between the two. Passes backward along the pterygoid canal and supplies the upper pharynx, the auditory tube and may contribute to the tympanic cavity, anastomosing with the other (anterior, posterior, superior and inferior) tympanic arteries
        5. Pharyngeal branch travels through the palatovaginal (pharyngeal) canal and supplies the roof of the nasopharynx, the auditory tube and the sphenoid sinus
        6. Sphenopalatine artery passes through the sphenopalatine foramen to reach the nasal cavity where it supplies the posterior and superior parts of the nasal septum, the lateral nasal wall and contributes to Kiesselbach’s plexus.

  1. Superficial temporal artery
    • The lesser of the terminal ECA branches usually emerging at the level of the neck of the mandible within the parotid gland. Ascends superficially over the posterior root of the zygomatic arch, passes just anterior to the ear and enters the temporal region travelling within the subcutaneous tissue of the scalp
    • Branches:
      1. Transverse facial artery emerges within the parotid gland and travels horizontally accross the face superficial to the masseter muscle. Supplies the parotid gland, masseter, facial muscles, and skin
      2. Anterior auricular branches supply the auricle and external acustic meatus
      3. Middle temporal artery pierces the temporalis fascia to supply the temporalis muscle
      4. Frontal branch ascends on the forehead and runs toward the midline. Supplies the forehead, scalp, and frontalis muscle
      5. Parietal branch courses posteriorly and superiorly and supplies the lateral scalp in the parietal region