Brain Circulation, Meninges & CSF Flashcards
Why does the brain have a high intake of cardiac output?
As it has high metabolic demand and a high demand for glucose
Why is the blood vessel structure circular (cerebral arterial circle) in the brain?
So that if one of the vessels is damaged/ cut off, the brain still has a sufficient blood supply.
What are the 4 possible routes into the cerebral arterial circle?
- Internal carotid artery
- Basilar artery
- Maxillary artery
- Vertebral artery
In dogs and horses, which vessel gives the largest proportion of the brain’s blood supply?
Internal carotid artery
(Small proportions are also supplied by the basilar artery)
In sheep, pigs and cats which blood vessel gives the largest blood supply to the brain?
The maxillary artery
Which arteries provide the largest blood supply to the brain in an ox?
Maxillary and vertebral arteries
How are the brain and meninges drained?
They are drained by veins and sinuses
What are the 3 sinuses in the brain?
- Dorsal sagittal sinus
- Straight sinus
- Ventral cavernous sinus
Where do these sinuses drain to?
Maxillary, vertebral, occipital and internal jugular veins
Where would you find the dorsal sagittal sinus?
Between the two hemispheres of the brain
What are the 3 meninges surrounding the brain and spinal cord?
Dura mater
Arachnoid mater
Pia mater
Describe the dura mater.
Tough and fibrous. Fused to the skull in the head
Where is the epidural space and why is it not present in the brain?
Epidural space is above the dura mater but is not present in the brain as it is tightly adhered to the skull.
What does the arachnoid mater consist of?
- Subarachnoid space containing cerebrospinal fluid
- Fine filaments connecting to the pia mater
What is the pia mater fused with?
Pia mater is fused with the neural tissue underneath
Meningeal folds = inward folding of dura mater. Where and what are the 2 meningeal folds?
- Falx cerebri (between cerebral hemispheres)
- Tentorium cerebelli (between cerebrum and cerebellum)
What are the 4 chambers of the ventricular system in the brain?
- A curved lateral ventricle in each cerebral hemisphere
- A ring-like third ventricle
- Fourth ventricle beneath the cerebellum
How are the ventricles in each cerebral hemisphere connected to the ring-like ventricle?
Via intraventricular foramen
How is the third ventricle connected to the fourth ventricle beneath the cerebellum?
Via mesencephalic aqueduct
What are ventricles ad what do they do?
Ventricles are cavities in the brain that produce and store CSF
What is CSF?
- CSF is an ultrafiltrate of blood mixed with secretions from ependymal cells lining the ventricles.
- CSF is clear and colourless and contains very few cells.
Complete the sentence:
CSF… is the same as blood plasma (it contains less K+ but more Cl- and glucose)
Osmolality
Why is the blood brain barrier important?
Protects the brain from substances that could be harmful.
What is the blood brain barrier (BBB) made of?
- Tight junctions between capillary and endothelial cells
- Thick basement membrane of the capillary
- Astrocyte processes surround capillaries
What areas of the brain lie outside the BBB?
The hypothalamus
Where does CSF end up once it has been removed from the subarachnoid space?
Enters venous blood circulation
How does the CSF enter the venous sinuses?
Via arachnoid villi
What is the clinical significance of the BBB?
- BBB is more permeable in developing and old animals compared with normal adults
- Some drugs cannot cross BBB
- Function of BBB can be compromised by inflammation -> must then be careful what drugs are given as they may enter brain
What happens to the pressure of CSF during pathological states?
Pressure elevates (this happens with meningitis or tumours)
CSF can be tapped for a sampe, what are the risks of this?
Tapping may do more harm than good if there is an excess of pressure within the fluid.
What are the two largest parts of subarachnoid space?
- Cerebromedullar cistern
- Lumbar cistern
