The Internal Carotid Artery - Podcast Version 0:00 / 0:00 1x 0.25x 0.5x 0.75x 1x 1.25x 1.5x 1.75x 2x The internal carotid artery is one of a pair of vessels that form a crucial component of the arterial supply to the brain. Together, the internal carotid arteries contribute to the anterior circulation, supplying the anterior aspects of the cerebrum – as well as the eye, forehead, and nose. In this article, we shall examine the anatomy of the internal carotid artery – its course, supply and clinical relevance. Pro Feature - 3D Model You've Discovered a Pro Feature Access our 3D Model Library Explore, cut, dissect, annotate and manipulate our 3D models to visualise anatomy in a dynamic, interactive way. Learn More Course The internal carotid artery arises as a terminal branch of the common carotid artery within the carotid triangle of the neck. Its origin is approximately at the level of the superior border of the thyroid cartilage (C4). The artery ascends within the carotid sheath, lying anterior to the transverse processes of the C3–C1 vertebrae. It then enters the cranial cavity via the carotid canal, which passes through the petrous part of the temporal bone. Within the carotid canal, the internal carotid artery is accompanied by the internal carotid nerve – a branch of the superior cervical ganglion carrying sympathetic fibres. These fibres form the internal carotid plexus around the artery. After entering the cranial cavity, the internal carotid artery passes through the cavernous sinus. On exiting, it gives rise to the ophthalmic artery, which passes through the optic canal to supply the eye, forehead and nose. Just inferior to the anterior clinoid processes of the sphenoid bone, the artery makes a sharp 180-degree turn. It then terminates by dividing into the anterior cerebral artery and middle cerebral artery, which contribute to the circle of Willis. By TeachMeSeries Ltd (2026) Fig 1Cervical course of the internal carotid artery. Carotid Sinus The carotid sinus is a dilatation of the proximal internal carotid artery (or distal common carotid artery) which contains baroreceptors innervated by the glossopharyngeal nerve (CN IX). These receptors detect changes in blood pressure, with an increase in pressure resulting in reflex slowing of the heart rate and vasodilation. Supply The internal carotid artery supplies the brain, as well as the orbit and surrounding structures. This is achieved via several major branches (in addition to smaller unnamed branches). The first major branch is the ophthalmic artery is the ophthalmic artery, which supplies the orbit and contributes to the forehead and nose: Forehead – supplied by the supraorbital and supratrochlear arteries Nose – supplied by the dorsal nasal and anterior ethmoidal arteries The internal carotid artery also gives rise to branches that contribute to the circle of Willis – including the anterior cerebral artery, middle cerebral artery, and posterior communicating artery. These vessels supply the majority of the cerebral hemispheres, with the anterior cerebral artery supplying the medial surfaces and the middle cerebral artery supplying the lateral surfaces. Lastly, the internal carotid artery also gives rise to the anterior choroidal artery, which supplies deeper structures of the brain. By TeachMeSeries Ltd (2026) Fig 2Structure of the circle of Willis. Clinical Relevance Carotid Sinus Hypersensitivity The carotid sinus is a dilatation located at the bifurcation of the common carotid artery, or at the proximal part of the internal carotid artery. It contains baroreceptors innervated by the glossopharyngeal nerve (CN IX), which detect changes in arterial blood pressure and help regulate cardiovascular reflexes. Carotid sinus hypersensitivity is an exaggerated response of these baroreceptors to stimulation. External pressure on the neck – such as tight collars, shaving, or head turning – can trigger an excessive reflex, resulting in marked bradycardia, vasodilation and a fall in blood pressure. This may lead to syncope or presyncope, particularly in older individuals. The condition highlights the clinical importance of the carotid sinus and its role in short-term blood pressure regulation. Do you think you’re ready? Take the quiz below Pro Feature - Quiz The Internal Carotid Artery Question 1 of 3 Submitting... Skip Next Rate question: You scored 0% Skipped: 0/3 1800 More Questions Available Upgrade to TeachMeAnatomy Pro Challenge yourself with over 1800 multiple-choice questions to reinforce learning Learn More Frequent questions What is the function of the internal carotid artery? The internal carotid artery is essential for supplying blood to the brain, as well as the eye, forehead, and nose. It contributes to the anterior circulation of the brain through its major branches, including the anterior and middle cerebral arteries. Where does the internal carotid artery originate? The internal carotid artery arises as a terminal branch of the common carotid artery, typically at the level of the superior border of the thyroid cartilage (C4). It ascends within the carotid sheath before entering the cranial cavity. What are the main branches of the internal carotid artery? The main branches of the internal carotid artery include the ophthalmic artery, anterior cerebral artery, middle cerebral artery, and anterior choroidal artery. These branches supply various structures, including the orbit and the majority of the cerebral hemispheres. What is the clinical significance of carotid sinus hypersensitivity? Carotid sinus hypersensitivity is an exaggerated response of baroreceptors in the carotid sinus to stimulation, which can lead to bradycardia and hypotension. This condition can result in syncope, particularly in older adults, highlighting the carotid sinus's role in regulating blood pressure. How does the internal carotid artery enter the cranial cavity? The internal carotid artery enters the cranial cavity through the carotid canal located in the petrous part of the temporal bone. It is accompanied by the internal carotid nerve, which carries sympathetic fibres and forms a plexus around the artery. Rate This Article