Student copy. Blood supply to the Brain 2025

Blood Supply Overview

Topic: Blood supply to the brain by Dr. U Offor

Key Arteries:

  • Carotid Arteries

  • External Carotid Arteries

  • Internal Carotid Arteries

  • Common Carotid Arteries

  • Vertebral Arteries

Considered Important Arteries:

  • Anterior Cerebral Artery

  • Middle Cerebral Artery (right and left)

  • Posterior Cerebral Artery

  • Basilar Artery

Circle of Willis:

  • Vital arterial anastomosis at the base of the brain

  • Includes anterior communicating artery and posterior communicating artery

Objectives:

  1. Describe the principal arteries of the brain and spinal cord.

  2. Explain collateral circulation possibilities through the Circle of Willis.

  3. Describe venous drainage of the brain and spinal cord.

  4. Discuss major vascular disorders in relation to functional loss.

General Facts About Brain Blood Supply:

  • Represents ~2% of body weight.

  • Receives 15% of cardiac output while using:

    • 20% of total body oxygen

    • 25% of total body glucose.

  • Average blood flow is 46 mL/100g of brain/min.

  • 20 seconds of anoxia causes unconsciousness; >5 minutes results in permanent unconsciousness.

  • Blood flow is auto-regulated.

  • Arteries: thin-walled, prone to blockage, distortion, or rupture.

  • Veins: thin-walled, lack valves, and no muscle/elasticity.

Arterial Supply Details:

  • Two systems supply the brain:

    • Anterior circulation: Internal carotid arteries (for anterior and middle brain areas).

    • Posterior circulation: Vertebrobasilar system supplies the hindbrain and occipital lobe.

  • Their branches anastomose on the brain's inferior surface, forming the Circle of Willis.

Arteries Pathway:

  • Anterior Arteries:

    • Internal Carotid Artery: Traverses through the carotid canal.

    • Carotid siphon: Passes through the cavernous sinus.

  • Posterior Arteries:

    • Vertebral Artery: Passes through the transverse foramina of C6-C1.

    • Basilar Artery: Formed by the union of vertebral arteries.

Anterior Circulation Branches:

  • Main Branches of Internal Carotid Artery (ICA):

    • Ophthalmic Artery: Supplies orbit and retina.

    • Posterior Communicating Artery: Connects carotid and vertebral arteries.

    • Middle Cerebral Artery: Supplies basal ganglia and internal capsule (lateral 2/3rd of cortex).

    • Anterior Cerebral Artery: Supplies medial aspects of frontal and parietal lobes; also anastomoses with MCA.

Cerebral Arterial Circle (Willis):

Key Structures Visible from the Inferior View:

  • Anterior Communicating Artery

  • Posterior Communicating Artery

  • Internal Carotid Artery

  • Middle Cerebral Artery

Posterior Circulation Branches:

  • Branches:

    • Vertebral Artery: Supplies spinal cord and dorsal medulla (PICA).

    • Basilar Artery: Supplies pons and cerebellum.

    • Posterior Cerebral Artery (PCA): Supplies inferior and medial aspects of the temporal and occipital lobes; thalamus and midbrain; anastomoses with MCA.

Circle of Willis Functionality:

  • Anastomosis: Connects vertebrobasilar and internal carotid systems.

  • Significance:

    • Ensures consistent blood flow and oxygen supply to the brain.

    • Provides collateral flow in cases of arterial occlusion.

Blood Supply to the Cortex:

  • Circle of Willis Structures:

    • Includes arteries such as the Middle Cerebral Artery, Posterior Cerebral Artery, and Anterior Communicating Artery.

  • Anterior Cerebral Artery (ACA):

    • Smaller terminal of ICA.

    • Supplies medial surface and deep structures of the cerebrum.

  • Middle Cerebral Artery (MCA):

    • Larger terminal branch of ICA.

    • Supplies superolateral surfaces and internal structures of the brain.

  • Posterior Cerebral Artery (PCA):

    • Terminal branch of basilar artery.

    • Supplies inferior surface of cerebrum and deep structures including thalamus and midbrain.

Blood Supply to Brainstem and Cerebellum:

  • Posterior Cerebral Artery: Supplies brainstem and cerebellum via branches.

Vertebral Artery Branches:

  • Branches to Supply:

    • Posterior spinal artery

    • Anterior spinal artery

    • PICA.

Basilar Artery Branches:

  • Supplies cerebellum and pons.

Spinal Cord Blood Supply:

  • Blood supply features of the spinal cord; illustrates anterior and posterior spinal arteries.

Collateral Circulation:

  • Circle of Willis:

    • Anterior and Posterior Communicating Arteries facilitate blood flow in case of ICA compromise.

  • Compensation Mechanisms:

    • Discuss how the vertebrobasilar system compensates when vascular occlusions occur.

Clinical Significance of Collateral Circulation:

  • Role in Stroke Management:

    • Importance of Circle of Willis integrity during ischemic events.

Venous Drainage of the Brain:

  • Characteristics:

    • No valves, extremely thin walls, organized into superficial, deep, and dural venous sinuses.

  • Superficial and Deep Veins:

    • Details on major superficial and deep veins and their drainage pathways.

  • Dural Venous Sinus Overview:

    • Includes locations, terminations, and whether they are single or paired.

Cavernous Sinus:

  • Anatomy and connections; drains into the internal jugular vein.

  • Structures in Cavernous Sinus:

    • Internal carotid artery and cranial nerves traversing the area.

  • Cavernous Sinus Clinical Significance:

    • Discusses Cavernous Sinus Thrombosis, ICA Aneurysms, and related symptoms.

Blood Supply to the Cerebral Cortex:

  • Overview of vascular distribution to functional areas of the cortex.

  • Cortical Functional Areas:

    • Detailed locations and functions of key cortical areas including motor and sensory strips, visual and language centers.

  • Functional Areas and Vascular Supply:

    • Regional supply from major arteries and corresponding infarction effects.

MCA Clinical Correlation:

  • Discussion of clinical implications of MCA strokes, including specific deficits.

Cerebrovascular Accidents:

  • Major causes of stroke, types, and pathophysiology of ischemic and hemorrhagic strokes.

Cerebral Aneurysms:

  • Types of aneurysms and risk factors associated with ruptures.

Types of Stroke Presentations:

  • Explains presentations for lacunar strokes versus cortical strokes, including clinical manifestations.

Conclusion:

  • Summary from Queen Mary University of London on vascular anatomy in relation to brain function.