Brain Vasculature Flashcards
The brain receives how much of the cardiac output and is responsible for how much O2 and glucose consumption?
15% of the cardiac output
20% of O2 consumption
25% of glucose consumption
How is the venous system set up to decrease the likelihood of increased intracranial pressure?
It is set up as a series of valveless sinuses with collateral channels
What is the main purpose of the cerebrospinal fluid?
To allow the brain to float in the skull
What are the meninges? List the three parts.
The meninges are a connective tissue covering that encloses and protects the brain and spinal cord. It is divided into the dura mater, the arachnoid mater, and the pia mater.
Describe the dura mater.
A tough, fibrous sack that surrounds the brain and has firm attachment points to the skull and sacrum. Creates the dural folds and venous sinus system of the brain.
Describe the arachnoid mater.
Named from it’s fine, web-liked appearance. Middle layer of the meninges. The CSF flows underneath this layer in the subarachnoid space. It also forms the arachnoid villi, which are responsible for resorbing CSF and returning it to the blood stream.
Describe the pia mater.
A very thin layer, adherent to the brain and spinal cord. Impermeable to fluid, this layer covers every surface of the brain except some areas of the ventricular system.
What are the four dural folds?
The falx cerebri located in the longitudinal fissure and separating the two hemispheres of the brain. The tentorium cerebelli which separates the cerebellum from the occipital lobe. The falx cerebelli which separates the cerebellar hemispheres. And the sellar diaphragm which covers the pituitary.
What is the function of the denticulate ligaments?
They are thin structures that emerge from the pia of the spinal cord and attach to the dura mater. They are thought to stabilize the motion of the spinal cord.
What structure is continuous with the pia mater and extends from the lowest tip of the spinal cord and anchors it at the sacrum and coccyx?
The filum terminale
How much CSF does the choroid plexus produce a day and how much suspends the brain and spinal cord at all times?
450-500ml produced a day with 150ml used
What is the pressure of the CSF?
10mmHg
How is CSF propelled?
By brain movements and pulsations of surface arteries
The brain weighs 1400g normally, but when suspended in CSF, how much does it weigh? What purpose does this serve?
It weighs 45g when suspended in CSF. It serves to prevent the cranial nerves and blood vessels from being crushed
The ventricles allow for what to occur?
They allow space for the CSF to move through.
What is the flow of the CSF?
CSF flows from the 3rd ventricle to the 4th ventricle via the cerebral aqueduct. From the 4th ventricle CSF passes down into the spinal canal or exits into the subarachnoid space. CSF enters the subarachnoid space by exiting the fourth ventricle through foramina of Luschka and Magendie. CSF then ascends to superior sagittal sinus to be reabsorbed by the arachnoid granulations.
What produces the CSF?
Choroid plexus
Where is the choroid plexus located?
It is located in the lateral, third and fourth ventricles
How is CSF drained?
The arachnoid villi filter the CSF into the superior sagittal sinus, effectively returning the CSF back into blood circulation.
What artery supplies most of the cerebral hemispheres?
The internal carotid artery
What artery ascends through the transverse foramina of vertebrae C1-6 (not C7)?
The vertebral artery
The basilar-vertebral system supplies what structures?
The spinal cord, brain stem, inner ear, cerebellum, occipital and temporal lobes
What two arteries converge to form the basilar artery?
The vertebral arteries located on the ventral side of the medulla
What four arteries branch off of the basilar artery?
The anterior inferior cerebellar, the pontine, the superior cerebellar, and the posterior cerebral arteries
What are the two major spinal arteries?
The vertebral artery and the radicular branches of intercostal arteries
What are the symptoms of occlusion from the anterior/posterior spinal arteries?
Loss of spinal cord function at level of occlusion (paralysis, loss of sensation, etc.)
What are the symptoms of occlusion from the posterior inferior cerebellar artery (PICA)?
Called Wallenberg syndrome. Loss of pain and temperature sensation on contralateral side of body/torso and ipsilateral side of face
What are the symptoms of occlusion from the anterior inferior cerebellar artery (AICA)?
Lateral pontine syndrome. Sudden onset vomiting/vertigo. Ipsilateral loss of sensation to face and ipsilateral facial paralysis
What are the symptoms of occlusion from the superior cerebellar artery?
Ipsilateral limb dysmetria and contralateral loss of sensation
What are the symptoms of occlusion from the pontine artery?
Contralateral paralysis and loss of sensation. Often results in death. Several outcomes possible depending on size of infarct.
What are the symptoms of occlusion from the labyrinthins artery?
Ipsilateral hearing loss and vertigo
What is the collective term of communicating vascular branches that form anastamoses between cerebral arteries?
The circle of willis
The circle of willis has two arteries that form the majority of the structure, what are they?
The anterior cerebral artery and the posterior communicating artery
The middle cerebral artery travels where?
Along the lateral fissure and lateral surface of cerebral cortex
What are the two areas of the middle cerebral artery that are at risk for strokes?
The cortical branches (which results in paralysis and sensory loss on contralateral side, with damage to the dominant side usually resulting in aphasia) and the lateral striate arteries (results in hemiplegia)
Where is the anterior cerebral artery located?
Along the medial surface of the cerebral cortex, including cingulate gyrus (part of limbic system)
If the anterior cerebral artery were occluded, what symptoms would present?
Paralysis and sensory loss in contralateral leg and foot. Also, abulia would present, which is defined as a lack of will or initiative. Has pronounced passivity, reduced social interaction, reduced emotional responsiveness, and reduced spontaneous motions
Where is the posterior cerebral artery located?
It projects to the occipital and temporal lobes.
If the posterior cerebral artery were occluded, what symptoms would arise?
Visual field defects, prosopagnosia - face blindness, contralateral deficits of the facial, vagus and hypoglossal nerve, and ipsilateral deficits of the oculomotor nerve
Describe the pathway of the venous drainage to the brain.
Blood from cerebral hemispheres and brain stem drain outwardly into surface veins. Cerebral veins drain venous blood into dural sinuses
What are the dural sinuses?
Venous compartments within the dura mater that convey venous blood. The meningeal dural layers form the falx cerebri and tentorium cerebelli
Where is the straight sinus located?
At the intersection of the falx cerebri and tentorium cerebelli and goes towards the thalamus
Where is the confluens located?
On the inside of the occipital bone at the intersection of the falx cerebri and tentorium cerebelli at the beginning of the straight sinus
The transverse sinus extends outward from the confluens along the intersection of the ______ and the interior surface of ______?
Tentorium cerebelli; the occipital bone
Sigmoid sinus is an extension of the transverse sinus that drops down into the jugular foramen and becomes the ______?
Internal jugular vein
What sinus lies on either side of the sphenoid?
The cavernous sinus
What plexus does the cavernous sinus communicate with that puts it at risk for transmitting infections to the brain?
The pterygoid plexus
The cavernous sinus drains into the ______ which then drains into the _____
Inferior and superior petrosal sinuses; transverse sinus
What structures pass inferiorly through the meningeal dural layer, through the sinus and then through the periosteal dural layer and then exit through foramina in the cranial base?
Internal carotid artery, CN III, IV, V, VI
What are the two venous structures of the spine?
The anterior and posterior longitudinal sinuses, and the basivertebral vein
The basivertebral vein is important in prostate cancer metastasizes because ____?
It is how prostate cancer metastasizes into the vertebrae
Emissary veins allow for what?
Emissary veins allow for thermoregulation by allowing venous blood to pass freely between scalp and dural sinuses.
The blood brain barrier consists of?
Endothelium, pericytes, astrocyte feet and basal lamina
What is the function of the BBB?
To prevent large, water soluble molecules from going into the brain
How do glucose and amino acids penetrate through the BBB?
Active transport; Oxygen and CO2 just go directly through lipid membranes
Where in the brain is there no BBB and why?
In the hypothalamus. This is to allow the passage of larger molecules since the hypothalamus controls many solute concentration in the body and monitors hormone levels along with ingested poisons (in order to stimulate the vomiting center)
