Lecture 5 - Blood & Meninges Flashcards
What are the two subsystems of the cerebrovascular system?
Atrial & Venous
The atrial system has what 3 structures, in order from largest to smallest?
Arteries, arterioles, capillaries
The venous system has what three structures, in order from smallest to largest?
Venules, veins, sinuses
What do the atrial and venous systems do?
Atrial System → supplies oxygenated blood to the brain
Venous System → removes deoxygenated blood from the brain back to the heart & lungs
Neurons are more/less sensitive to oxygen deprivation than other cells
More
Deprivation of blood to the brain for 4-6 mins results in what?
Irreversible brain damage
Systolic vs Diastolic
Systolic - pressure away from the heart
Diastolic - passive return of blood towards the heart
The internal carotid system contains what two types of arteries?
Anterior cerebral arteries & middle cerebral arteries
What are the two main systems of blood supply of the brain?
Internal carotid system & Vertebrobasilar system
What are the 5 main inputs of the cerebrovascular system?
Vertebral arteries
Basilar artery
Circle of willis
Posterior cerebral arteries
Internal Carotid
The vertebrobasilar system contains _______ arteries as well as _________
Cerebellar
Right & left vertebral arteries
The right and left vertebral arteries form the ______ artery at the level of the pons
Basilar
Where do each of the 4 main inputs of the cerebrovascular system supply the blood to?
Vertebral arteries - posterior parts of brain + cerebellum & brainstem
Basilar artery - posterior brain & brainstem
Circle of willis - collateral circulation (ensures blood flows even if one part of system is compromised)
Posterior cerebral arteries - occipital lobes
Internal Carotid - major cerebral artery!!!
What are the branches of the internal carotid artery? Where do they supply blood to?
Anterior cerebral arteries - medial portions of the frontal lobe & superior medial parietal lobes
Middle cerebral arteries - lateral portions of brain (inclu. parts of frontal, temporal & parietal lobes)
What are the two types of cerebral veins?
Superficial & deep
What is the role of the superior cerebral veins? Where does the blood drain?
Receives deoxygenated blood from the cortical surfaces (drains superior, lateral & medial surfaces of the hemispheres)
Drain into the superior and inferior sagittal sinus, the straight sinus and transverse sinus
What is the role of the deep cerebral veins? Where does the blood drain?
- Drain the deep structures of the brain (e.g. white matter & basal ganglia)
- Converge on the internal cerebral veins (inferior sagittal sinus above 3rd ventricle)
- Form the great cerebral vein
- Continues into the straight sinus and the sigmoid sinus
What are the four sinuses of the cerebral venous system?
Superior sagittal
Inferior sagittal
Straight
Transverse
Which of the 4 sinuses is the largest?
Superior sagittal
Which of the sinuses is located at the base of the brain (posterior and superior to the cerebellum)?
Straight sinus
The transverse sinus is bilateral, lateral to the cerebellum, and runs in grooves of the _____ bone & _____ portion of the temporal bone
Occipital, squamous
The inferior sagittal sinus drains which venous system? The medial aspect of which lobe? Which gryus?
Superficial cerebral
Frontal
Cingulate
What is the blood-brain barrier? What are its purposes?
What: Interface capillaries with surrounding brain tissue
Purposes: Protect brain against toxic substances &
Protect against abnormal variations in concentration of ions and molecules
What are the 3 cortical arteries?
Anterior cerebral
Middle cerebral
Posterior cerebral
The anterior cerebral artery travels in the interhemispheric fissure along the corpus callosum and stops where?
Occipital lobe
The anterior cerebral arteries supplies blood to the ____ and _____ for which body parts?
Sensory & motor cortices, feet & legs
T/F The middle cerebral artery is the smallest of the cortical arties
F. It’s the largest
The middle cerebral artery supplies blood to the sensory and motor cortices for which body parts? What other structures does it supply blood to?
Arms, hands, face
Parietal lobe, premotor area, broca’s area, basal ganglia
The posterior cerebral artery splits from the basilar artery to go laterally to _______ and caudally to ________
Inferior temporal lobe
Occipital lobe
Additionally to the inferior temporal lobe & the occipital lobe, what other structures does the posterior cerebral artery supply blood to?
Thalamus & midbrain
What is a CVA?
Cerebrovascular Accident “stroke” - brain cells die because they are deprived of oxygen and glucose
What are the two main types of strokes?
Ischemic/occlusive & hemorrhagic
Within occlusive strokes, what are the 3 subtypes?
Transient Ischemic Attacks (TIA) → temporary interruption of blood flow for a few minutes to an hour
Thrombotic (50%) → when a blood clot (thrombus) forms in an artery that supplies blood to the brain, typically at a site of atherosclerosis (narrowing of the artery due to plaque buildup)
Embolic (30) → when a blood clot or debris (embolus) forms elsewhere in the body (such as the heart or another artery) and travels through the bloodstream to lodge in a cerebral artery, blocking blood flow
What is a hemorrhagic stroke?
a blood vessel ruptures, causing bleeding (hemorrhage) into or around the brain
What is an occlusive stroke?
Happens when an artery supplying blood to the brain becomes blocked, reducing blood flow (ischemia). This type of stroke is the most common.
What is the difference between intracerebral & extracerebral hemorrhage?
Intracerebral hemorrhage: Bleeding occurs within the brain tissue itself
Extracerebral hemorrhage: Bleeding occurs within the meninges
What are the 3 types of extracerebral hemorrhage?
Subarachnoid hemorrhage: Bleeding occurs in the space between the brain and the thin tissues covering it (subarachnoid space).
Subdural –under dura mater
Epidural –under the skull
What are Arteriovenous Malformations?
Abnormal tangles of blood vessels connecting arteries and veins, which can rupture and cause hemorrhagic strokes.
- AVMs are a congenital condition, but they may remain unnoticed until they cause problems such as seizures, headaches, or a hemorrhage.
How many meninges are in the brain?
3
What are the purposes of the meninges? (4)
- Maintain the brain in a fluid suspension/cushion
- Holding structures in place during movement
- Provide nutrients (CSF)
- Passageway for blood vessels (arachnoid mater)
What are the 3 meningeal layers called, from outermost-innermost?
Dura mater
Arachnoid mater
Pia mater
Which meningeal layer is the toughest? Which one is considered “tender”?
Dura, pia
What are the layers of the dura mater? Where are they?
The periosteal layer (which is attached to the skull) and the meningeal layer (which is continuous with the spinal dura mater)
The dura mater forms ________, which collect venous blood from the brain and direct it towards the _______ veins
Dural sinuses, internal jugular
What is the space beneath the arachnoid mater called? What is it filled with? What else does it contain?
Subarachnoid space, cerebrospinal fluid (CSF) Contains major blood vessels
The arachnoid mater acts as what?
Shock absorber
The ____ mater is transparent and thin
Pia
Which meningeal layer does not peel off well from the brain? Why?
Pia
It closely adheres to the brain’s contours, following its folds and grooves
What is the space between the outer layer of the dura mater and inner surface of the skull/vertebral canal known as?
Epidural space
What is the space between the dura mater and arachnoid mater known as?
Subdural space
What is the space between the arachnoid mater and pia mater known as?
Subarachnoid space
What is cerebrospinal fluid? Where is it?
A clear, colorless fluid that fills the subarachnoid space and circulates around the brain and spinal cord.
What is a hematoma?
An abnormal collection of blood that forms outside of blood vessels, usually after a hemorrhage has occurred.
What are the 3 main functions of the cerebrospinal fluid?
Cushioning: Provides a protective cushion for the brain and spinal cord, absorbing shocks from movements or trauma.
Nutrient Supply: Delivers essential nutrients and removes waste products from the brain.
Pressure Regulation: Helps maintain intracranial pressure and provides buoyancy to the brain
What are the two types of hematoma? Where do they occur?
Epidural Hematoma: Occurs between the skull and the dura mater.
Subdural Hematoma: Occurs between the dura mater and the arachnoid mater.
How many ventricles do we have? What do they do?
4
Circulate cerebrospinal fluid
What are the 4 ventricles called?
2 lateral
3rd ventricle
4th ventricle
How is the ventricle system interconnected to the subarachnoid space?
Through the foramen in the 4th ventricle
Which ventricle(s) have an anterior horn, a posterior horn & an inferior horn?
The lateral ventricles!
What is the function of the lateral ventricles?
Produce a significant portion of the brain’s CSF through the choroid plexus, a network of blood vessels within the ventricles.
The CSF flows from the lateral ventricles into the third ventricle via the interventricular foramen (foramen of Monro).
Where is the third ventricle?
A narrow, midline cavity located between the two halves of the thalamus. (diencephalon)
What is the function of the third ventricle?
It receives CSF from the lateral ventricles and contains choroid plexus that contributes to CSF production.
How does the CSF flow from the 3rd to the 4th ventricle?
Goes through the cerebral aqueduct
Where is the fourth ventricle?
Situated between the brainstem (pons and medulla oblongata) and the cerebellum.
How does CSF exit the fourth ventricle and enter the subarachnoid space?
The median aperture (foramen of Magendie) in the midline.
The lateral apertures (foramina of Luschka) on each side.
CSF acts a ______ and protects the _____ and _______ from excessive de/acceleration
Cushion, brain & spinal cord
The CSF is an active transport system to participate in removal of _______ and _____. This is then reabsorbed by the _____ _____ that dump into the ______ sinus
Harmful substances & waste
Arachnoid granulations
Superior sagittal
T/F The draining of CSF is a pressure sensitive process dependent on production
F. Independent of production
What is hydrocephalus?
- Hydrocephalus results from increased fluid but less drainage and increased intracranial pressure
- Caused by + production of CSF, - reabsorption of CSF, or – drainage.
- Enlarged ventricles and enlarged cranium in children because skull bones haven’t fused yet (fontanelles).
