3- Blood Supply and Meninges Flashcards
What percentage of the total body weight is made up by the brain?
2%
What percentage of total oxygen inspired does the brain consume ?
20%
What is a stroke?
Decreased blood supply to the brain over a long period of time
How common is a stroke in over 65s?
1 in 100
What are the 2 pairs of arteries that supply the brain called?
- Vertebral artery
2. Internal carotid artery
What is the vertebral artery a branch of?
The subclavian artery
What joins the vertebral and Internal carotid arteries?
The circle of Willis at the base of the brain
Where does the vertebral artery ascend?
Ascend in the neck through transverse foramen of the cervical vertebrae
Enters the skull the skull via the foramen magnum
What do the vertebral arteries do once they enter the skull?
They fuse forming the Basilar artery
The Internal carotid artery is a branch of what?
Our common carotid artery
How does the internal common carotid artery enter the skull?
Via the carotid canal
Name the branches of the vertebral artery that supply the spinal cord
Anterior spinal artery
Posterior spinal artery
When are the anterior and posterior branches formed?
Prior to the vertebral arteries fusing in the skull
What does the vertebral artery branch into prior to fusing?
- The anterior spinal artery
- The posterior spinal artery
- The posteriors inferior cerebellar artery
What does The posteriors inferior cerebellar artery supply?
The posteriors inferior cerebellum
What does the basilar artery branch into?
- Anterior inferior cerebellar artery (AICA)
- Pontine artery
- Superior cerebellar arteries
- Posterior cerebral artery
What does The Anterior inferior cerebellar artery supply?
The anterior inferior cerebellum
What does the pontine artery supply?
Supply the pons
What does the superior cerebellar artery supply?
the superior aspect of the cerebellum
Why is the posterior cerebral artery called the instead of cerebellar?
Because it goes to the back of the cerebrum
Name the branches of the internal common carotid artery
- Middle cerebral artery
2. Anterior cerebral arteryW
What forms the circle of Willis?
The closing of the middle and anterior cerebral arteries into a circle
Name the 3 pairs of cerebral arteries
Post. Cerebral
Middle Cerebral
Ant. Cerebral
Name the 3 pairs of cerebellar arteries
Post. Inf . Cerebellar
Ant. Inf. Cerebellar
Sup. Cerebellar
What does the circle of willis do?
Interconnects the internal carotid and vertebral – basilar system
What does the circle of willis surround?
Surrounds optic chiasm and hypothalamus
What does the circle of willis ensure?
Ensures that blood flow doesn’t decrease if any of the arteries are blocked
What is a berry Aneurysm?
Abnormal dilations around the circle of Willis or at the points of arterial branching within the brain
What can Berry Aneurysms cause?
If they rupture they can lead to a vascular stroke
What percentage of strokes are caused by berry aneurysms?
10%
What does the anterior cerebral artery (ACA) supply ?
- Superior and medial areas of frontal and parietal lobes
2. Corpus callosum
What does the middle cerebral artery (MCA) supply ?
Lateral areas of frontal, temporal and parietal lobes
What does the posterior cerebral artery (PCA) supply ?
Occipital lobe
Inferior and medial surface of temporal lobe
Which artery is affected if their is a lesion in the primary auditory cortex
MCA
Which artery is affected if their is a lesion in the primary visual cortex
PCA as it is in the occipital lobe
What are deep/perforating arteries?
Other smaller beached off the arterial circle
What are is another name for the deep arteries?
Striate arteries (delicate)
What do deep/ perforating/ striated arteries supply?
- Deep nuclei
- Deep grey matter
- Internal capsule
- Supply Includes major descending motor pathway
What is the internal capsule
Made up of white matter
It Is the major fibre bundle to and from cerebral cortex
If their was an injury to any of the striate arteries what could happen
You might experience some motor deficits
Where is all the blood from the brain drained into?
The internal jugular veins
What are meninges?
Protecting airbags
How many layers of meninges do we have and what are they called?
We have 3 layers:
- Dura mater
- Arachnoid mater
- Pia mater
What do the meninges cover?
The central nervous system:
The brain and spinal cord
What is the first layer of meninges called?
Dura mater
Describe the dura mater
It is a tough fibrous layer that surrounds and protects the brain
Name the meninges under the dura mater
The arachnoid mater
Describe the arachnoid mater
It is shiny and translucent
It is thin and delicate
Spider weblike
Very vascular
What is the inner most later of meninges called?
The Pia mater
Describe the Pia mater
It is very thin
It is tightly applied into the surface of the brain and cervix of the spinal cord
Cant really be separated
What path does the Pia mater follow?
Follows the cortex of the brain and follows the sulk and gyri of the brain
What is special about the dura mater?
It has 2 layers:
The outer periosteal layer of dura
The Inner meningeal layer of dura
What is the outer periosteal layer of the dura?
It is firmly attached to the bone of the skull
What is the inner meningeal layer of the dura?
It is firmly attached to the arachnoid
What is the space between the arachnoid and Pia called?
The Subarachnoid space
What is found in the Subarachnoid space?
cerebrospinal fluid (CSF)
Are both the layers of the dura mater attached to each other?
Yes apart from at certain points
What do the 2 layers of dura allows
For dural infoldings (partitions) only at specific areas
What forms as a result of dural infoldings?
A space between the outer and inner layer of the dura mater called a dural sinus
What are found in the dural sinuses?
Venous blood
Which dural infolding separates the 2 hemispheres?
The Faix cerebri
What can happen if a vessel in the brain bursts?
Can suffer from a haemorrhage
What happens an artery bursts between the periosteal layer and the skull?
The patient can suffer from a Epidural haemorrhage (hematoma)
The bursting of which artery can lead to an epidural haemorrhage?
A torn meningeal artery
What happens a blood vessel bursts between the meningeal dura and the arachnoid?
Accumulation of blood causing a subdural haemorrhage
The bursting of which vessel can lead to a subdural haemorrhage?
Torn bridging vessels
What happens a blood vessel bursts in the subarachnoid space
Accumulation of blood causing a subarachnoid haemorrhage
The bursting of which vessel can lead to a Subarachnoid haemorrhage?
Torn cerebral arteries
Where is the Falx cerebri found?
Between the cerebral hemispheres
Where is the Tentorium cerebelli found?
between occipital lobes and cerebellum
Name some sinuses found in the brain?
- Superior sagittal sinus
- Transverse sinus
- Inferior sagittal sinus
Where are Dural Venous Sinuses found?
Located within the dural infoldings
Where do dural venous sinuses receive blood from?
Little superficial veins
Where does the superior sagittal sinus empty blood into?
To the confluence of sinuses
Where does the inferior sagittal sinus empty blood into?
The straight sinus
Where do Deep veins empty blood into?
The great cerebral vein and the straight sinus
Once in the straight sinus where does all the blood go?
Into the. confluence of sinus
Once in the confluence of sinuses where does all the blood go?
Into the transverse sinus
What does our transverse sinus become?
The sigmoid sinus
Where does the sigmoid sinus drain blood into?
Our internal jugular veins
Briefly describe the pathway of venous drainage starting at the superficial veins
- Superficial veins
- Superior sagittal sinus
- Confluence of sinuses
- Transverse sinuses
- Sigmoid sinus
- Internal jugular veins
Briefly describe the pathway of venous drainage starting at the deep veins
- Deep veins
- Internal cerebral veins
- Straight sinus
- Confluence of sinuses
- Transverse sinuses
- Sigmoid sinus
- Internal jugular veins
Name the 3 meninges of the spill cord
- Dura mater
- Arachnoid
- Pia
What is found between the dura and the vertebrae (SPINAL CORD)?
The epidural space occupied by fat
What is found in the sub arachnid space?
Cerebral spinal fluid
What is the pia firmly attached to in the spinal cord?
The cord
What projects out of the Pia?
Denticulate ligaments
What do Denticulate ligaments
do?
They anchor the spinal cord
What is found in our ventricular system?
Fluid filled cavities
Name the 5 ventricles in out brain?
- Lateral ventricle
- Third ventricle
- Cerebral aqueduct
- Fourth ventricle
- Central canal
What does the central canal make upon an adult brain?
he ventricular system as it fils up with fluid
What connects our lateral ventricle to our third ventricle?
The interventricular foramen
foramen of Monroe
What connects our 4th ventricle to our 3rd ventricle?
The cerebral aqueduct
What connects our 4th ventricle to the rest of the subarachnoid space?
2 Lateral apertures (foramina of Luschka)
and a Median aperture (foramen of Magendie)
What does the lateral ventricle follow?
The shape of the brain
Where is the 3rd ventricle located?
Between the 2 thalami
Where is the 4th ventricle located?
Between the pons and the cerebellum
Why are ventricles formed in the brain?
due to the enormous growth and distortion an elaborate system of ventricles are formed.
What do ventricle develop as?
dilations from the central canal of the embryological neural tube
Name the 4 ventricles that make up the brain
2 x lateral ventricles
3rd ventricle:
4th ventricle:
Where are the 2 lateral ventricles located?
one within each cerebral hemispheres. Follow c-shape of hemispheres.
What do the ventricles all contain?
Contain choroid plexus which produce CSF
What allows CSF to escape the ventricular system and where does it go?
Series of apertures allow CSF to escape ventricular system into subarachnoid space
Briefly describe the schematic view of the ventricular system
- Lateral ventricles
- Interventricular foramen
- 3rd ventricle
- Cerebral aquaduct
- 4th ventricle
- Lateral and median apertures
- Subbarachnoid space
Describe Cerebrospinal fluid (CSF)
it is a clear and colourless solution
What is CSF derived from and where is it made?
The blood
Produced in ventricles by specialised areas of ventricular lining: choroid plexus
What is CSF contain?
Contains glucose and inorganic salts, little protein, few cells.
What does CSF fill?
Fills subarachnoid space and ventricular system of brain.
Why is the CSF important?
It Provides physical protection and chemical stability for CNS
Where is CSF made?
The choroid plexus
in each ventricle
Which cells filtrate blood an produces CSF?
Ependyma cells
Describe the path CSF takes
- Lateral ventricle
- Foramina of Monroe
- Third ventricle
- Cerebral aquaduct
- Fourth ventricle
- Foramina of Luschka and Magendie
- Sub arachnid space
- Reabsorbd into sinuses
How is CSF reabsorbed into the sinuses?
Via the arachnoid granulations (villi)
What are arachnoid granulations (villi)?
extensions of arachnoid matter into dural sinuses
predominantly the superior sagittal sinus
What happens if we have a blockage in the CFS drainage system?
More CSF will produced than drained leading to build CSF
This results in hydrocephalus
What can hydrocephalus cause?
Build up pressure in the skull
what can hydrocephalus cause in children?
Expansion of the skull as pressure builds up in the brain
What do doctors do to try and treat Hydrocephalus?
They insert a needle into the ventricles to remove some of the CSF liquid and hope to reduce pressure in the skull
How much CSF is produced daily?
About 500ml/day.
What are the 4 functions of CSF?
- Buoyancy: Brain and spinal cord float to reduce traction
- Cushioning effect to dampen trauma
- Transport of substances: Nutrients, dissolved gasses, removal of metabolites
- Provides stable environment
What supplies the Inferior and medial surface of temporal lobe?
The posterior cerebral arteries
What is the epidural space occupied by?
Fat
Through which foramen does the vertebral artery enter the skull?
The foramen magnum
What do the anterior and posterior spinal arteries supply?
The spinal cord
What supplies the Superior and medial areas of frontal and parietal lobes?
The anterior cerebral artery
What supplies the Lateral areas of frontal, temporal and parietal lobes?
The middle cerebral arteries
What supplies the posteriors inferior cerebellum?
The posteriors inferior cerebellar artery
What supplies the Anterior inferior cerebellum?
The anterior inferior cerebellar artery (AICA)
What supplies the pons?
The pontine arteries
What empties blood to the straight sinus?
The inferior sagittal sinus and the deep veins
What is the space between the occipital loves and the cerebellum called?
The Tentorium cerebelli
What supplies the superior aspect of the cerebellum?
The superior cerebellar artery
Name the clinical condition associated with Abnormal dilations around the circle of Willis?
Berry aneurysm
What is the space between the cerebral hemispheres called?
The Falx cerebri
What supplies the Corpus callosum?
The anterior cerebral artery
What causes 10% of vascular strokes?
Berry aneurysms
What supplies the Occipital lobe?
The posterior cerebral arteries
What is the Subarachnoid space?
The space between the arachnoid and pia
What is a dural sinus?
Space between the inner and outer dura mater formed due to dural infoldings
What empties blood to the confluence of sinuses?
The superior sagittal sinus
What empties blood into the great cerebral vein?
Deep veins
What is the epidural space?
Space between the dura and vertebrae in the spinal cord
What are Denticulate ligaments?
They are projections from the pia that anchor the spinal cord
What is the foramen of Monroe?
An intraventricular foramen that connect the lateral ventricle to the third ventricle
What is the cerebral aqueduct?
It connects our 3rd ventricle to our 4th ventricle
What does the choroid plexus produce?
Cerebrospinal fluid (CSF)
What is hydrocephalus?
When there is a blockage somewhere in the CSF drainage system resulting in more CSF being produced than reabsorbed
What does CSF stand for?
Cerebrospinal fluid (CSF)
