Carotid Artery | Anatomy2Medicine
Carotid Artery,

Carotid Artery

      • Is a branch of the brachiocephalic trunk on the right
      • arises directly from the arch of the aorta on the left.
      • Is divided into three parts by the anterior scalene muscle

 

  • the first part passes from the origin of the vessel to the medial margin of the anterior scalene

 

        • the second part lies behind this muscle

 

  • third part passes from the lateral margin of the muscle to the outer border of the first rib.

 

      • Its branches include the following:

 

  • Vertebral Artery

 

          • Arises from the first part of the subclavian artery
          • ascends between the anterior scalene and longus colli muscles.
          • Ascends through the transverse foramina of vertebrae C1 to C6

 

  • passes through the foramen magnum into the cranial cavity.
  • Thyrocervical Trunk

 

          • Is a short trunk from the first part of the subclavian artery
          • divides into the following arteries:

 

  • Inferior Thyroid Artery
  • arches downward to the lower pole of the thyroid gland.
  • Gives rise to an ascending cervical artery, which ascends medial to the phrenic nerve.
  • Transverse Cervical Artery
  • Suprascapular Artery

 

            • Passes superior to the superior transverse scapular ligament, whereas the suprascapular nerve passes inferior to this ligament.

 

  • Internal Thoracic Artery

 

          • Arises from the first part of the subclavian artery,
          • descends through the thorax behind the upper six costal cartilages,

 

  • ends at the sixth intercostal space by dividing into the superior epigastric and musculophrenic arteries.
  • Costocervical Trunk

 

          • Arises from the posterior aspect of the second part of the subclavian artery
          • divides into the following arteries:

 

  • Deep Cervical Artery
  • Superior Intercostal Artery
  • gives rise to the first two posterior intercostal arteries.
  • Dorsal (Descending) Scapular Artery

 

          • Arises from the third part of the subclavian artery

 

  • Surgical Anatomy of  Subclavian Artery branches

 

      • Neurovascular compression (thoracic outlet) syndrome
      • produces symptoms of nerve compression of the brachial plexus and the subclavian vessels.
      • It is caused by
        • abnormal insertion of the anterior and middle scalene muscles (scalene syndrome)
        • by the cervical rib
      • Subclavian steal syndrome
        • a cerebral and brain stem ischemia
        • caused by reversal of blood flow from the basilar artery through the vertebral artery into the subclavian artery
        • occurs in the presence of occlusive disease of the subclavian artery proximal to the origin of the vertebral artery.

 

  • When there is very little blood flow through the vertebral artery, it may steal blood flow from the carotid, circle of Willis, and basilar circulation and divert it through the vertebral artery into the subclavian artery and into the arm

 

      • causes vertebrobasilar insufficiency and thus brain stem ischemia and stroke.
      • Symptoms are dizziness, ataxia, vertigo, visual disturbance, motor deficit, confusion, aphasia, headache, syncope, arm weakness, and arm claudication with exercise.
      • It can be treated by a carotid-subclavian bypass.

 

    • Common Carotid Arteries
          • right common carotid artery, begins at the bifurcation of the brachiocephalic artery
          • left common carotid artery, arises from the aortic arch (MCQ)

 

  • Ascend within the carotid sheath

 

          • divide at the level of the upper border of the thyroid cartilage into the external and internal carotid arteries.(MCQ)

 

  • Receptors
  • Carotid Body

 

              • Lies at the bifurcation of the common carotid artery as an ovoid body.
              • Is a chemoreceptor
              • control respiration.
              • stimulated by chemical changes in the circulating blood
                • lack of oxygen
                • excess of carbon dioxide,
                • increased hydrogen ion concentration
              • Is innervated by the

 

  • nerve to the carotid body which arises from the pharyngeal branch of the vagus nerve

 

                • carotid sinus branch of the glossopharyngeal nerve.

 

  • Carotid Sinus

 

              • Is a spindle-shaped dilatation
              • located at the origin of the internal carotid artery
              • functions as a pressoreceptor (baroreceptor),
              • stimulated by changes in blood pressure.

 

  • When stimulated, it causes a slowing of the heart rate, vasodila- tion, and a decrease in blood pressure.

 

              • Is innervated
                • primarily by the carotid sinus branch of the glossopharyngeal nerve

 

  • by the nerve to the carotid body of the vagus nerve.

 

              • Carotid sinus syncope results from hypersensitivity of the carotid sinus,
        • Internal Carotid Artery
          • Has no branches in the neck (MCQ)
          • ascends within the carotid sheath in company with the vagus nerve and the internal jugular vein

 

  • enters the cranium through the carotid canal in the petrous part of the temporal bone.
  • Is separated from the tympanic cavity by a thin bony structure.

 

          • Lies within the cavernous sinus and gives rise to small twigs to the
            • wall of the cavernous sinus
            • hypophysis
            • semilunar ganglion of the trigeminal nerve.
          • Pierces the dural roof of the cavernous sinus between the anterior clinoid process and the middle clinoid process, which is a small projection posterolateral to the tuberculum sellae.
          • Forms a carotid siphon just before it enters the cranial cavity.

 

  • Ophthalmic Artery

 

            • Enters the orbit via the optic canal with the optic nerve

 

  • Posterior Communicating Artery
  • Arises from the carotid siphon and joins the posterior cerebral artery.
  • Runs backward below the optic tract and supplies the optic chiasma and tract and hypothalamus.
  • Anterior Choroidal Artery

 

            • Supplies the choroid plexus of the lateral ventricles, optic tract and radiations, and lateral geniculate body.

 

  • Anterior Cerebral Artery

 

            • supplies the optic chiasma and medial surface of the frontal and parietal lobes of the brain, and unites each by the short anterior communicating artery.

 

  • Middle Cerebral Artery
  • Passes laterally in the lateral cerebral fissure and supplies the lateral convexity of the cerebral hemisphere.
  • External Carotid Artery

 

            • Extends from the level of the upper border of the thyroid cartilage to the neck of the mandible,

 

  • it ends in the parotid gland by dividing into the maxillary and superficial temporal arteries.

 

            • Has eight named branches

 

  • Superior Thyroid Artery

 

            • Gives rise to an infrahyoid, sternocleidomastoid, superior laryngeal, cricothyroid, and several glandular branches.

 

  • Lingual Artery

 

            • Arises at the level of the tip of the greater horn of the hyoid bone and passes deep to the hyoglossus to reach the tongue.
            • Gives rise to suprahyoid, dorsal lingual, sublingual, and deep lingual branches.

 

  • Facial Artery

 

 

            • Hooks around the lower border of the mandible at the anterior margin of the masseter to enter the face.

 

  • Ascending Pharyngeal Artery

 

            • Gives rise to pharyngeal, palatine, inferior tympanic, and meningeal branches.

 

  • Occipital Artery

 

            • Arises from the posterior surface of the external carotid artery, just above the level of the hyoid bone.

 

  • Sternocleidomastoid Branch

 

              • Anastomoses with the sternocleidomastoid branch of the superior thyroid artery.

 

  • Descending Branch
  • Its superficial branch anastomoses with the superficial branch of the transverse cervical artery.
  • Its deep branch anastomoses with the deep cervical artery of the costocervical trunk.
  • Posterior Auricular Artery

 

            • Gives rise to stylomastoid, auricular, and occipital branches.

 

  • Maxillary Artery

 

            • large terminal branch of the external carotid artery.

 

  • Superficial Temporal Artery

 

            • small terminal branch of the external carotid artery.
            • Gives rise to the transverse facial artery
        • Vertebral Arteries
          • Arise from the first part of the subclavian artery

 

  • ascend through the transverse foramina of the vertebrae C1 to C6.
  • enter the cranial cavity through the foramen magnum.

 

          • Join to form the basilar artery

 

  • Branches
  • Anterior Spinal Artery
  • Posterior Spinal Artery
  • Posterior–Inferior Cerebellar Artery

 

        • BasilarArtery

 

  • formed by the union of the two vertebral arteries at the lower border of the pons.
  • Ends near the upper border of the pons by dividing into the right and left posterior cerebral arteries.
  • Branches
  • Pontine Arteries
  • Labyrinthine Artery

 

              • Enters the internal auditory meatus
              • supplies the cochlea and vestibular apparatus

 

  • Anterior–Inferior Cerebellar Artery

 

              • Gives rise to the labyrinthine artery in 85% of the population

 

  • Superior Cerebellar Artery
  • Posterior Cerebral Artery

 

              • Is formed by bifurcation of the basilar artery
              • supplies the midbrain and the temporal and occipital lobes of the cerebrum.
          • Circle of Willis (Circulus Arteriosus) Is formed by the

 

  • posterior cerebral
  • posterior communicating
  • internal carotid
  • anterior cerebral,

 

          • anterior communicating arteries.