Blood Supply of the CNS
Lecture Objectives
• Describe the four arteries supplying the CNS.• Follow up each artery to its destination. • Describe the circle of Willis and its branches.• Discuss the principle of end artery type of circulation.• Describe venous drainage of the brain.
Vertebral Artery• Branch of the 1st part of the subclavian a.
• Ascends the neck through the upper sex transverse vertebrae
• Inters the skull through foramen magnum
• Both sides unit to form the basilar a.
Vertebral Artery
• Branches• Meningeal aa.• Anterior spinal a. • Posterior spinal aa.• Posterior inferior cerebellar a.• Medullary aa.
Basilar Artery
• Ascend in front of pons • Participate in forming circle of Willis
• Branches • Anterior inferior cerebellar aa.• Pontine aa.• Superior cerebellar aa.• Posterior cerebral aa. (end branches)• Inferior & posterior parts of cerebrum
Blood Supply to CortexCircle of Willis
Blood Supply to CortexVascular Territories
Blood Supply to CortexVascular Territories
Blood Supply to CortexVascular Territories
Blood Supply to Deep Structures
Internal Carotid Artery
• Ophthalmic a.• Posterior communicating a.• Anterior choroidal a.• Anterior cerebral a.• Middle cerebral a.
Middle Cerebral Artery
• Language areas (left MCA in most people)• Motor & somatosensory cortex (except‐ lower limb & perineum)• Auditory cortex• Lenticulostriate arteries‐ basal gangila & internal capsule (genu)
Middle Cerebral Artery
Middle Cerebral Artery
Anterior Choroidal Artery
• Hippocampus, uncus & amygdala• Choroid plexus (temporal horn of lateral ventricle• Globus pallidus, putamen, part of thalamus• Internal capsule (posterior limb)
Anterior Choroidal Artery
Anterior Cerebral Artery
• Motor & somatosensory cortex (lower limb & perineum)• Corpus callosum (except‐ splenium)• Olfactory bulb & tract• Recurrent artery of Heubnar
• Head of caudate (ventral part) and adjacent putamen• Internal capsule (anterior limb)
Anterior Cerebral Artery
Posterior Cerebral Artery
• Hippocampus• Parahippocampal gyrus• Calcarine branch‐ all primary & some association cortex for vision• Posterior choroidal artery
• Choroid plexus (lateral & 3rd ventricles)• Thalamus (posterior part)• Fornix• Tectum
Posterior Cerebral Artery
Blood Supply to SC• One anterior spinal a.
• Vertebral aa.• Two posterior spinal aa.
• Vertebral aa. 25%• PICA 75%
• Anterior & posterior radicular aa.• Arise at every spinal level• Serve their respective roots & ganglia
Blood Supply to SC
• Anterior & posterior spinal medullary aa.• Arise at intermittent levels• Serve to augment the BS to SC
• Artery of Adamkierwicz• Unusually large spinal medullary a.
• Usually on the left• In low thoracic or upper lumber levels
Blood Supply to SC• Spinal cord Ischemia• Anterior spinal a.
• Small & tenuous• Occlusion produces bilateral damage (below lesion)
• Affects• Corticospinal tracts
• Paraplegia below lesion• Spinothalamic tracts
• Thermoanesthesia and analgesia
• Descending autonomic tracts• Loss of bladder & bowel
control• Anterior gray horn
• Near enlargement – weakness of limb muscles
Veins of the BrainSuperior cerebral veins → SSS
Superficial middle cerebral veins → cavernous sinus
Deep middle cerebral veinAnterior cerebralStriate veins
basal vein
Thalamostriate veinChoroid vein
Internal cerebral vein
Great cerebral vein↓
straight sinus
External cerebral veins Internal cerebral veins
Veins of the Brain
Veins of the Brain
Dural Venous Sinuses
LocationDrains …..Fate• Superior sagittal sinus
• Venous lacunae• Inferior sagittal sinus• Straight sinus• Occipital sinus• Transverse sinus• Sigmoid sinus• Cavernous sinuses• Superior and inferior petrosal sinuses
Dural Venous Sinuses
Blood Brain Barrier
• protects cells from some toxins and pathogens• proteins & antibiotics can not pass but alcohol & anesthetics do
• Structure• tight junctions seal together epithelial cells
• continuous basement membrane• astrocyte processes covering capillaries
Blood Brain Barrier
• Areas without BBB• Area postrema in the floor of the fourth ventricle
• Areas in the hypothalamus
• Structure• Endothelial fenestrations
Blood Cerebrospinal Fluid Barrier
• Structure• Endothelial cells• BM of endothelial cells• Pale cells• BM of choroidal epithelial cells• Tight junctions seal the choroidalepithelial cells