Anatomy of the Internal Carotid Artery

Internal Carotid Artery (ICA)

• Originates at the bifurcation of the common carotid artery in the neck, at the level of the upper border of the thyroid cartilage
• Divided into four parts: cervical, petrous, cavernous, and cerebral

Cervical Part

• Located within the carotid sheath
• Passes vertically upward to the base of the skull

Petrous Part

• Enters the skull through the carotid canal
• Runs horizontally, forwards, and medially inside the petrous part of the temporal bone
• Ascends vertically and curves forwards to enter the cranial cavity via the foramen lacerum

Cavernous Part

• Pierces the posterior wall of the cavernous sinus
• Runs forwards inside the cavity of the sinus with the abducent nerve
• Curves upwards to pierce the roof of the sinus at the anterior clinoid process
• Branches:
  • Carotico-tympanic artery to the middle ear cavity
  • Supra and inf. hypophyseal arteries to the pituitary gland
  • Meningeal branches to the meninges of the middle cranial fossa
  • Branches to the trigeminal ganglion

Cerebral Part

• Emerges from the roof of the cavernous sinus, medial to the anterior clinoid process
• Runs backwards above the cavernous sinus, but below the optic nerve
• Bends upwards to reach the base of the brain at the anterior perforated substance
• Ends by dividing into two terminal branches: anterior and middle cerebral arteries
• Branches:
  • Ophthalmic artery
  • Anterior cerebral artery
  • Middle cerebral artery
  • Posterior communicating artery
  • Anterior choroidal artery

Ophthalmic Artery

• Originates as a branch of the cerebral part of the ICA
• Enters the orbit through the optic canal, inferolateral to the optic nerve
• Pierces the dura mater, crosses above the optic nerve, and runs along the medial wall
• Terminates near the medial angle of the eye by dividing into supratrochlear and dorsal nasal arteries
• Branches:
  • Central artery of the retina
  • Posterior ciliary arteries
  • Muscular branches to ocular muscles
  • Lacrimal branch to the lacrimal gland
  • Medial palpebral arteries to the upper and lower eyelids
  • Posterior ethmoidal artery to ethmoidal air sinuses and nasal cavity
  • Anterior ethmoidal artery
  • Supraorbital artery
  • Supratrochlear artery
  • Dorsal nasal artery

Anterior Cerebral Artery (ACA)

• Originates as a terminal branch of the internal carotid artery
• Runs towards the longitudinal fissure, communicating with the other anterior cerebral artery through the anterior communicating artery
• Runs backwards over the corpus callosum, terminating at the parieto-occipital sulcus by anastomosing with the posterior cerebral artery
• Branches:
  • Cortical branches: supply medial surface (except occipital lobe), lateral surface (1-inch strip superiorly), and inferior surface (medial part of orbital surface)
  • Central branches: antero-medial set (AM) pierces the anterior perforated substance, supplying the anterior part of the caudate, lentiform nucleus, and internal capsule (genu and lower half of the anterior limb)

Middle Cerebral Artery (MCA)

• Originates as a terminal branch of the internal carotid artery
• Runs in the lateral sulcus and insula to reach the superolateral surface

This quiz covers the origin, course, and parts of the internal carotid artery, including its path through the neck and skull. Test your knowledge of this crucial blood vessel.