4. CNS Blood Supply

What are the four systems that protect and support the CNS?

Meninges, cerebrospinal fluid (CSF), blood vessels, blood-brain barrier

What are the three meningeal layers (from inner to outer)?

Pia mater, arachnoid mater, dura mater

Which meningeal layer lies directly on the brain surface?

Pia mater

Where is the CSF located?

In the ventricles and cisterns

What are the ventricles?

Fluid-filled spaces entirely within brain tissue

What are cisterns?

CSF-filled spaces between the pia and arachnoid mater

Where do arteries enter the CNS?

In the subarachnoid space (between pia and arachnoid)

Where does venous blood drain from the brain?

Through venous sinuses into the jugular veins

What is the blood-brain barrier (BBB)?

A cellular layer with tight junctions that regulates substance entry into the brain

What two systems supply arterial blood to the brain?

Anterior and posterior circulations

Which artery provides anterior circulation to the brain?

Internal carotid artery (ICA)

What arteries branch from the ICA?

Anterior cerebral artery (ACA) and middle cerebral artery (MCA)

Which artery provides posterior circulation to the brain?

Vertebral arteries → form the basilar artery

What arteries branch from the basilar artery?

Posterior cerebral arteries (PCA)

What does the ACA supply?

Medial frontal and parietal lobes

What does the MCA supply?

Lateral frontal, parietal, and temporal lobes

What does the PCA supply?

Occipital lobe and inferior temporal lobe

What connects anterior and posterior circulations?

Posterior communicating arteries (PComm)

What connects the two anterior cerebral arteries?

Anterior communicating artery (AComm)

What is the Circle of Willis?

A ring of arterial anastomoses at the brain’s base

Why is the Circle of Willis important?

Provides collateral flow if one artery is blocked

What structures are supplied by small perforating arteries?

Basal ganglia, thalamus, internal capsule

What arteries supply the internal capsule’s genu and posterior limb?

Lenticulostriate arteries (off the MCA)

What arteries supply the thalamus and posterior limb of internal capsule?

Thalamic perforating arteries (off the PCA)

Why are lenticulostriate arteries vulnerable to damage?

They branch directly from high-pressure vessels and are prone to hypertensive injury

What artery supplies the anterior two-thirds of the spinal cord?

Anterior spinal artery

Where does the anterior spinal artery originate?

From branches of the vertebral arteries before they form the basilar artery

What does the anterior spinal artery supply?

Corticospinal tract and spinothalamic tract

What symptoms result from anterior spinal artery occlusion?

Weakness and loss of pain/temperature sensation

What arteries supply the posterior third of the spinal cord?

Posterior spinal arteries

Where do the posterior spinal arteries come from?

Branches of the vertebral arteries in the cervical spine

What tract is affected by posterior spinal artery occlusion?

Dorsal columns

What symptoms result from posterior spinal artery occlusion?

Loss of touch, vibration, and proprioception

Why can’t the anterior and posterior spinal arteries supply the entire cord?

They are too small to supply the full length

What artery supplements blood flow to the caudal spinal cord?

Artery of Adamkiewicz

Where does the artery of Adamkiewicz arise?

From the aorta, usually at T4–T8

What part of the cord does the artery of Adamkiewicz supply?

Thoracic and lumbosacral segments

What does occlusion of the artery of Adamkiewicz cause?

Ischemia of caudal cord → lower extremity diplegia

What artery supplies the medial medulla?

Anterior spinal artery

What arteries supply the lateral medulla?

Posterior inferior cerebellar artery (PICA) and vertebral arteries

What other artery may contribute to upper lateral medulla?

Anterior inferior cerebellar artery (AICA)

What supplies the medial pons?

Small pontine perforating arteries from the basilar artery

What supplies the lateral pons and middle cerebellar peduncle?

Anterior inferior cerebellar artery (AICA)

What supplies the medial midbrain?

Perforating arteries from the basilar artery

What supplies the tegmentum of the midbrain?

Posterior cerebral artery (PCA)

What supplies the tectum of the midbrain?

Superior cerebellar artery (SCA)

What is the tegmentum?

The midbrain region anterior to the cerebral aqueduct

What is the tectum?

The midbrain region posterior to the cerebral aqueduct

What layer surrounds the CNS and contains venous sinuses?

Dura mater

What is the dura mater?

A thick, tough outer connective tissue layer around the CNS

What forms the dural venous sinuses?

Folds and separations in the dura mater

What does the falx cerebri separate?

The two cerebral hemispheres

What does the tentorium cerebelli separate?

The cerebrum and cerebellum

Where are the superior and inferior sagittal sinuses located?

Inside the falx cerebri

Where are the transverse sinuses located?

Inside the tentorium cerebelli

What do the sagittal sinuses drain into?

Confluence of sinuses

Where does blood flow after the confluence of sinuses?

Transverse sinuses → sigmoid sinuses

Where do the sigmoid sinuses drain?

Into the internal jugular veins

What is the function of the dural venous sinuses?

Drain venous blood from the brain into the jugular system