1.1Brain Circulation, Meninges and C.S.F Flashcards
Where is blood circulated?
From the heart –> head –> will be supplied by various vessels both to the
- Structure of the head
- Brain
which carotids supply the brain, main blood supply?
internal carotids
which carotids supply structure in the head
external carotids
Is a main blood vessel, comes from the right subclavian artery?
common carotids
Important for measuring levels of oxygen and, controlling pressure to the brain.
carotid body and sinus
whats another name for the Cerebral arterial circle (CAC)?
Circle of Willis
CAC:
blood arrives here before distributed to the brain, supplies form the central region
Can the internal caratoid arteries be seen?
No, but the stumps of cartoid arteries can be seem
What is the basiler artery responsible for?
It brings blood to the CAC
What does a cow not have?
internal carotid
What is the basilar artery responsible for?
It brings blood to the CAC
Vertebral artery:
- runs of either side of the artery
- contribute to CAC
- in cased in vertebrae
What is the figure highlighted?
Basilar artery
What animals do NOT have an internal carotid artery?
cats and ruminants
In the dog, man, and horse what supplies the circle of Willis and most parts of the brain
- Internal Carotid
- Basilar Artery
In dogs, man, and horse what artery supplies the rest of the brain?
verterbral artery
In sheep and cat what artery supplies the CAC and has rete mirabile?
maxillary artery
what is the rete mirabile?
arrangement of capillaries before blood vessel joins main blood supply
In sheep and cat what artery supplies the medulla oblongata (hindbrain)
vertebral artery
In sheep and cat what does the basilar do differently?
drains away from CAC
In the cow what does the basilar do differently?
drains away
In the cow what artery supplies the CAC?
maxillary and vertebral
Why cant you slice a cows neck with a knife?
because the vertebral will continue to supply the CAC and cow will still be conscious
What do the veins in the brain NOT have and why?
They dont have valves, this allows for complete flow without hinderance
Venous drainage of the brain:
- cerebral veins lack valves
- drain to venous sinuses of dura mater
brain circulation volume:
20% cardiac output goes to the brain because need for high oxygen and nutrinets
Anything less than 20% = supply
autoregulation:
mechanism uncertain
sympathetic regulation:
restricted –> little activity for blood vessels in brain
Where are anasetics injected?
always in the epidural never below the dura mater.
What are the 3 layers around the brain?
- Dura Mater
- Arachnoid mater
- Pia Mater
dura mater:
outer / toughest layer
arachnoid mater:
middle layer
Pia mater:
inner layer, visable, forms inner surface of brain
What is between the dura mater and archnoid mater?
Subdural space
what is between the Arachnoid mater and pia mater?
subarachnoid space
vertebral bone:
considerable epidural space around cord, unlike the brain
completely separate, doesn’t adhere to the vertebral column
Where does the epidural space lie?
between the periosteum and dura in vertebral canal
what does the epidural space contain?
loose connective tissue, veins, lymphatics
What does the epidural space contribute to the cord?
It cushions the cord as it flexes
What can the epidural space be used for?
nerve blocks:
- epidural injected on top of dura mater so it spreads slowly into the tissue area
**If spread fast would cause shock
Falx cerebri:
midline fold between cerebral hemispheres
Tentorium cerebelli:
oblique transverse fold between cerebrum and cerebellum
Diaphragma sellae
forms a collar around the neck of the pituitary so forms the roof of the hypophyseal fossa
Where does the subdural space lie between?
between the dura and arachnoid matter
Subdural space =
- potential space containing only lymph-like fluid
- site of subdural haematomata
When one gets a concussion where would the blood be found?
in the subdural space
What forms the falx?
The dura mater increases in between to form falx
subsarachnoid space:
- between the arachnoid and pia
- Contains CSF leaking from ventricular system
What the largest parts of the subarchnoid space?
Cisterns:
1. cerebellomedullary cistern
2. Lumbar cistern
cerebellomedullary cistern
found around foramen magnum, used in the collection of CSF
Lumbar cistern
used for lumbar puncture/collection of CSF
Pia mater characteristics:
highly vascular connective tissue, very closely applied to brain tissue
Where is CSF produced?
in all ventricles (especially the 4th) by choroid plexuses
What is CSF?
- Ultrafiltrate + some modification by ependymal cells lining ventricles
- clear & colorless - very few cellsin normal CSF
- osmolarity = plasma
whta is the CSF fluid volume in a dog?
25ml
Where can CSF pressure be elevated?
in meningitis, tumours
bloody and cellular CSF indicate?
injury
The blood-brain barrier:
- CNS capillary endothelium joined by tight junctions - all fluid must pass through cells (NOT hypothalmus)
-Also basal lamian covered by proceses of astrocytes
blood-brain barrier in summary:
tightly controlled, won’t expand suddenly, locate din brain tissue NOT outside
The blood-CSF barrier:
ependymal epithelium joined by tight junctions in choroid plexi - all fluid must pass through cells
