Cerebral Blood Flow Overview

Cerebral Blood Flow

• The presentation discussed cerebral blood flow, outlining arteries, veins, and cerebrospinal fluid (CSF) elements.

Outline

• Blood, arteries, blood-brain barrier, and blood flow regulation were covered.
• Veins, cerebrospinal fluid and sinuses, meninges, folds, spaces, CSF, and ventricles were included.
• Pathology included hemorrhage, ischemia, stroke characteristics, regions, and syndromes, along with other pathologies.

Arteries and Veins Outside the Skull

• Common Carotid A. passes through carotid canal and branches to internal carotid A.
• Subclavian A. passes through transverse foramen, including C1, and branches to vertebral A.
• Internal Jugular V. drains to Brachiocephalic v. and further to Superior Vena Cava.
• Diagram of arteries and veins outside the skull was included, including specific vessel labels (ICA, ECA, CCA, AICA, PICA, vertebral).

Brainstem Arteries

• Vertebral A. branches into Basilar A. and Posterior Spinal A. (x2).
• Basilar A. gives rise to posterior cerebral A., superior cerebellar A., pontine A., anterior inferior cerebellar A., posterior inferior cerebellar A., and anterior spinal A.

Spinal Arteries and Veins

• Anterior and Posterior Spinal A. are discussed, arising from the Basilar and Vertebral A.
• Anterior and Posterior Medullary A. reinforce spinal A.
• Intercostal A. supplies blood to spinal A.
• Epidural Venous Plexus is part of venous drainage system.

Circle of Willis

• The Circle of Willis includes 5 arteries in total.
• Internal Carotid A., Middle Cerebral A., and Anterior Cerebral A. are key arteries.
• Anterior Communicating artery connects bilateral anterior cerebral arteries.
• Basilar A. branches into Posterior Cerebral A.
• Posterior Communicating A. connects middle and posterior cerebral A.

Summary of Posterior and Anterior Circulation

• Posterior circulation involves Vertebral A. and Basilar A. leading to A.ICA, PICA, and posterior cerebral and pontine arteries.
• Anterior circulation describes Internal Carotid A. supplying Middle Cerebral A., Anterior Cerebral A., and Anterior Communicating A.
• Spinal circulation encompasses Anterior Spinal A. and Posterior Spinal A., reinforced by Medullary A. and fed by Intercostal A.

Penetrating Arteries

• Arteries are located in the subarachnoid space.
• Perivascular spaces surround penetrating arteries as they enter pia mater.
• Brain capillaries have tightly controlled junctions.
• Brain capillaries are fenestrated as part of the systematic capillaries.

Blood Brain Barrier

• Penetrating arteries are surrounded by glial cells forming the blood-brain barrier.
• Astrocytes maintain the neurochemical environment of the brain.
• Tight junctions control entry from the blood.
• Active transport moves large molecules through the blood-brain barrier.
• The blood-brain barrier protects the brain from infection, inflammation, and toxins.
• The blood-brain barrier allows free passage of O2, CO2, and other lipid-soluble substances.
• Astrocytes regulate ion, neurotransmitter, and hormone use.

Circumventricular Organs

• Exceptions to the blood-brain barrier allow sampling of blood flow and secretion of neuropeptides.
• These organs are located near the hypothalamus, 3rd ventricle, and 4th ventricle.
• Examples include neurohypophysis, pineal gland, and other circumventricular organs.

Imaging & Changes in Blood Flow

• Autoregulation adjusts blood flow based on neurotransmitters, metabolic activity, oxygen, glucose, and pH.
• Astrocytes, circumventricular organs, assist with autoregulation.
• Glucose and oxygen demands increase from brainstem to cortex, affecting metabolic demand in various brain regions.
• Intracranial pressure increases, leading to decreased blood flow.

Summary of Cerebral Blood Flow

• Penetrating arteries enter through perivascular space and are surrounded by astrocytes.
• Blood-brain barrier limits exchange of large molecules.
• Circumventricular organs sample blood via specialized cells.
• Autoregulation adaptively controls blood and nutrient distribution.

Veins and Cerebrospinal Fluid (CSF)

Dural Sinuses

• Superficial Cerebral V. drains into Bridging V. and Superior Sagittal Sinus within the Falx Cerebri.
• Deep Cerebral V. drains into Bridging V., Inferior Sagittal Sinus, and Straight Sinus.
• Deep veins drain basal ganglia, diencephalon, and white matter.
• Bridging Veins cross the meninges.

Sinus Confluence

• All sinuses converge at the confluence of sinuses.
• Confluence occurs at the junction of the falx and tentorium.
• Transverse sinus is within the tentorium cerebelli and drains into the sigmoid sinus.
• Sigmoid sinus drains into the Internal Jugular V.

Summary of Veins and CSF

• Superficial cerebral veins drain into bridging veins and major sinuses.
• Deep cerebral and bridging veins drain into inferior and straight sinuses.
• The sinuses converge at the confluence of sinuses and drain into the internal jugular vein.

Dura Mater

• Tough, two-layered membrane (periosteal and meningeal) adhering to the skull and arachnoid mater.
• Three major folds include falx cerebri, tentorium cerebelli, and falx cerebelli.
• Important for blood vessel passage, and drainage and protection processes.

Arachnoid Mater

• Delicate membrane between dura and pia mater.
• Subarachnoid space is filled with cerebrospinal fluid (CSF).
• Arachnoid trabeculae connect arachnoid to pia mater.
• Arachnoid granulations filter CSF into venous circulation.

Pia Mater

• Thin layer adhering to the brain's surface.
• Denticulate ligaments and filum terminale anchor the pia mater to the dura mater.
• Lumbar cistern, a CSF-filled space, is present at the spine's base.

Layers and Spaces

• The skull, epidural space, dura mater, subdural space, arachnoid mater, subarachnoid space, and pia mater comprises the layers and spaces of the brain.
• These crucial structures serve as protective layers and channels for CSF, blood vessels, and nutrients.

Summary of Meninges

• Dura Mater is a tough, layered membrane affixed to the skull.
• Arachnoid Mater is a delicate weblike membrane with projections linking to the Pia Mater and forming the subarachnoid space for CSF.
• Pia Mater is located adhering to the brain's surface, creating a protective layer between CSF and brain tissue.

Choroid Plexus and CSF

• Specialized cells surround capillaries floating within all ventricles.
• CSF produced by choroid plexus contains glucose, protein, and electrolytes.
• CSF cushions and protects the brain and spinal cord.

Lateral Ventricles

• Paired within the right and left hemispheres.
• Composed of anterior horn, posterior horn, inferior horn, and atrium.
• Connect to the third ventricle.

Third and Fourth Ventricles

• Third ventricle sits between the thalami, connected to the fourth ventricle by the cerebral aqueduct.
• Fourth ventricle is near the brainstem and cerebellum, with connections to the subarachnoid space through foramina of Lushka and Magendie.
• Both contain choroid plexus and circumventricular organs.

Ventricles

• Choroid Plexus floats in ventricles, producing CSF through specialized capillaries.
• CSF flows throughout the brain's lateral ventricles, third ventricle, and fourth ventricle, before exiting into the subarachnoid space.

This quiz covers the key aspects of cerebral blood flow, exploring the anatomy of arteries and veins, as well as the role of cerebrospinal fluid. It addresses blood flow regulation, pathology related to hemorrhage and ischemia, and provides insights into the vascular structure outside the skull and brainstem. Test your knowledge on essential vascular elements and their functions in the brain.