Right Common Carotid Artery

• It is a branch of the brachiocephalic artery.
• It begins in the neck behind the right sternoclavicular joint.

Left Common Carotid Artery

• It is a branch of the arch of the aorta.

• The carotid body is a small, oval, reddish-brown structure.
• It is situated behind the bifurcation of the common carotid artery.
• It receives a rich nerve supply mainly from the:
  • Glossopharyngeal nerve
  • Also from the vagus and sympathetic nerves
• It acts as a chemoreceptor.
• It responds to changes in the oxygen, carbon dioxide and pH content of the blood.

1. Course

The external carotid artery runs in the:

1. Carotid triangle
2. Digastric triangle
3. Then in the substance of the parotid gland.

2. Beginning and Termination

• It begins in the carotid triangle at the level of the upper border of the thyroid cartilage.
• This is opposite the disc between the 3rd and 4th cervical vertebrae.
• It runs upwards and slightly backwards and laterally.
• It terminates behind the neck of the mandible by dividing into:
  • Maxillary artery
  • Superficial temporal artery

3. Relation to Internal Carotid Artery

• The external carotid artery has a slightly curved course.
• In its lower part → it is anteromedial to the internal carotid artery.
• In its upper part → it is anterolateral to the internal carotid artery.

4. Relations in Carotid Triangle

• In the carotid triangle, the external carotid artery is comparatively superficial.
• It lies under cover of the anterior border of the sternocleidomastoid.
• It is crossed superficially by:
  • Cervical branch of the facial nerve
  • Hypoglossal nerve
  • Facial vein
  • Lingual vein
  • Superior thyroid vein

Structures Deep to the Artery

• Wall of the pharynx
• Superior laryngeal nerve, which divides into:
  • External laryngeal nerve
  • Internal laryngeal nerve
• Ascending pharyngeal artery

5. Relations Above the Carotid Triangle

• Above the carotid triangle, the external carotid artery lies deep in the substance of the parotid gland.
• Within the gland, it is related superficially to:
  • Retromandibular vein
  • Facial nerve

Structures Deep to the External Carotid Artery

1. Internal carotid artery
2. Structures passing between the external and internal carotid arteries:
   • Styloglossus
   • Stylopharyngeus
   • Both arise from the styloid process
   • IX nerve
   • Pharyngeal branch of X nerve
3. Two structures deep to the internal carotid artery:
   • Superior laryngeal nerve
   • Superior cervical sympathetic ganglion

• It is a small branch that arises from the medial side of the external carotid artery.
• It arises very close to the lower end of the external carotid artery.
• It runs vertically upwards between:
  • Side wall of the pharynx
  • Tonsil
  • Medial wall of the middle ear
  • Auditory tube

Branches

1. Pharyngeal Branches

Supply:

• Pharynx
• Tonsil
• Pharyngeal ends of auditory tube
• Soft palate

2. Inferior Tympanic Branch

• Supplies the medial wall of the tympanic cavity.
• These branches enter the middle ear through a canaliculus for the tympanic branches of the glossopharyngeal nerve.

3. Meningeal Branches

Enter the cranial cavity through:

1. Foramen lacerum
2. Jugular foramen
3. Hypoglossal canal

• It arises from the external carotid artery just below the level of the greater cornua of the hyoid bone.
• It runs downwards and forwards, parallel and just superficial to the external laryngeal nerve.
• It passes deep to the three long infrahyoid muscles to reach the upper pole of the lateral lobe of the thyroid gland.

Branches

1. Infrahyoid Branch

Runs along the lower border of the hyoid bone.

2. Superior Laryngeal Artery

• Pierces the thyrohyoid membrane along with the internal laryngeal nerve.
• It supplies the larynx.

3. Cricothyroid Branch

Anastomoses with similar branches of the opposite side.

4. Sternocleidomastoid Branch

Supplies the sternocleidomastoid muscle.

5. Terminal Branches

The superior thyroid artery divides into:

• Anterior branch
• Posterior branch

These supply the thyroid gland.

• The lingual artery arises from the external carotid artery just below the level of the greater cornua of the hyoid bone.
• It arises opposite the tip of the greater cornua of the hyoid bone.
• It is tortuous in its course.
• Its course is divided into three parts by the hyoglossus muscle.

Course

1. First Part

• Lies in the carotid triangle.
• Forms a characteristic upward loop.
• The loop is crossed by the hypoglossal nerve.
• The lingual loop permits free movements of the hyoid bone.

2. Second Part

• Lies deep to the hyoglossus along the upper border of the hyoid bone.
• It is superficial to the middle constrictor of the pharynx.

3. Third Part

• Called the arteria profunda linguae, or deep lingual artery.
• Runs upwards along the anterior border of the hyoglossus.

4. Fourth Part

• Finally, the artery runs horizontally forwards on the undersurface of the tongue as the fourth part.
• It is accompanied by the lingual nerve.

Branches

1. Suprahyoid Artery

Passes along the upper border of the hyoid bone.

2. Dorsal Lingual Artery

• 3–4 in number.
• Arises from the second part of the artery.

Supplies:

• Dorsal surface of tongue
• Palatine tonsil
• Soft palate

3. Sublingual Artery

• Arises from the third part.

Supplies:

• Sublingual gland
• Floor of the mouth

• The facial artery arises from the external carotid just above the tip of the greater cornua of the hyoid bone.
• It runs upwards:
  • First in the neck as the cervical part
  • Then on the face as the facial part
• The course of the artery in both places is tortuous.

Cervical Part

• The cervical part of the facial artery runs upwards on the superior constrictor of pharynx.
• It lies deep to:
  • Posterior belly of the digastric
  • Stylohyoid
  • Ramus of the mandible
• It grooves the posterior end of the submandibular salivary gland.
• The artery then makes an S-bend (two loops):
  • First winding down over the submandibular gland
  • Then up over the base of the mandible

Branches from Cervical Part

1. Ascending Palatine Artery

• Arises near the origin of the facial artery.
• Ascends upward between:
  • Styloglossus
  • Stylopharyngeus
• Winds around the upper border of the superior constrictor.
• Supplies:
• Tonsil
• Soft palate
• Pharynx
• Auditory tube

2. Tonsillar Artery

• It is the chief supply of the tonsil.
• It pierces the superior constrictor to reach the tonsil.

3. Glandular Branches

Supply the submandibular gland.

4. Submental Artery

• Accompanies the mylohyoid nerve.
• Runs along the lower border of the mandible.

Facial Part

• The facial part of the facial artery enters the face at the anteroinferior angle of the masseter muscle.
• It runs upwards close to:
  • Angle of mouth
  • Side of nose
  • Medial angle of eye

• The occipital artery arises from the posterior aspect of the external carotid artery.
• It arises opposite the origin of the facial artery.
• It is crossed by the hypoglossal nerve.

Branches

1. Sternomastoid Branches

• Upper sternomastoid branch → accompanies the spinal accessory nerve.
• Lower sternomastoid branch → loops around the hypoglossal nerve.

2. Mastoid Branch

• Enters the mastoid foramen.
• Supplies:
• Mastoid air cells
• Meninges

3. Meningeal Branches

Enter the cranial cavity through:

• Jugular foramen
• Condylar canals

4. Muscular Branches

Muscular branches are given.

5. Descending Branch

• Superficial branch → anastomoses with the superficial branch of the transverse cervical artery.
• Deep branch → anastomoses with the deep cervical artery.

6. Occipital Branches

Supply the scalp.

• The posterior auricular artery arises from the posterior aspect of the external carotid artery just above the posterior belly of the digastric.
• It runs upwards and backwards:
  • Deep to the parotid gland
  • Superficial to the styloid process
• It crosses the base of the mastoid process.
• It ascends behind the auricle.

Branches

1. Stylomastoid Branch

• Enters the stylomastoid foramen.
• Supplies:
• Middle ear
• Mastoid antrum
• Air cells
• Facial nerve

2. Auricular Branch

Supplies the auricle.

3. Occipital Branch

Supplies the scalp.

• It is the smaller terminal branch of the external carotid artery.
• It begins behind the neck of the mandible under cover of the parotid gland.
• It runs vertically upwards.
• It crosses the root of the zygoma or preauricular point, where its pulsations can be easily felt.
• About 5 cm above the zygoma, it divides into:
  • Anterior branch
  • Posterior branch

Branches

1. Transverse Facial Artery

• Arises from the superficial temporal artery within the parotid gland.
• Passes forwards along with the zygomatic branch of the facial nerve.
• Supplies:
• Parotid gland
• Temporomandibular joint
• Face

2. Anterior Auricular Branch

Supplies:

• Auricle
• External acoustic meatus

3. Zygomatico-orbital Branch

Supplies the face.

4. Middle Temporal Artery

• Pierces the temporal fascia.
• Supplies the temporalis.

5. Anterior and Posterior Divisions

Supply:

• Temple
• Scalp
• Auricle