Cerebral Vasculature Flashcards
What’s the function of the blood-brain barrier?
Separates brain tissue from blood circulation
- Maintain constant intracerebral chemical environment
- Control of entry of cells & molecules
- Protect against osmotic change
How does the blood-brain barrier do its job?
Tight junctions in blood vessel endothelium
Basement membrane
Astrocyte foot processes and pericytes
What are astrocytes?
Star shaped glial cells in the brain and spinal cord
What are pericytes?
Contractile cells that wrap around the endothelial cells of capillaries and venules of brain
What is a glial cell?
Non-neuronal cells that maintain homeostasis, form myelin, and provide support and protection for neurons in the brain and peripheral nervous system.
Name the 4 main arteries that supply the brain.
L&R vertebral arteries
L&R internal carotid arteries
Where do the vertebral arteries arise from?
Subclavian arteries
Describe the journey of vertebral arteries from Subclavian to brain.
Subclavian > ascend up posterior side of neck through holes in transverse processes of the cervical vertebrae (foramen transversarium) > cranial cavity via foramen magnum
Name 3 branches of the vertebral arteries and name their destination.
Meningeal branch - falx cerebri
Ant and Post spinal arteries - entire length of spinal cord
Post Inf cerebellar artery - cerebellum
What happens to the vertebral arteries after the branches have branched off?
Converge to form basilar artery
What do branches of basilar artery supply?
Cerebellum and pons
What does the basilar artery bifurcate into?
Post cerebral arteries
Where do the internal carotids originate from?
Where the left and right common carotids bifurcate - at C4
How do the internal carotids enter the skull?
Via carotid canal of temporal lobe
Name 3 branches of the internal carotid arteries and what they each supply.
Ophthalmic artery - structures of orbit
Posterior communicating artery - anastomotic connecting vessel in COW
Anterior cerebral artery - cerebrum
What happens to the internal carotid arteries after the branches have branched off?
They become the middle cerebral artery which supplies the lateral cerebrum
Name the three main constituents of the COW and the two connecting vessels.
Main:
Ant cerebral arteries
Internal carotid arteries
Post cerebral arteries
Connecting:
Ant communicating
Post communicating
Draw and label the COW.
:)
Name the three cerebral arteries! And say what lobes of the cerebrum they supply
Anterior - medial part of frontal lobes, superior medial part of parietal lobes
Middle - lateral part of temporal, frontal, parietal
Posterior - occipital, inferior part of temporal
What is an aneurysm?
A localised permanent dilation of a blood vessel
What is a berry aneurysm?
An aneurysm that occurs at the bifurcation of branches of the Circle of Willis. Forms a sac/berry shape.
It’s when the muscular arterial wall is replaced with fibrosis.
Leads to a subarachnoid haemorrhage.
Symptom of berry aneurysm?
Sudden thunderclap headache
What is a TIA?
Transient Ischaemic Attack - mini stroke where symptoms clear up within 24 hours
What is a CVA?
Cerebrovascular accident - stroke vascular lesion causing irreversible loss of central nervous tissue
Types of Strokes? Explain them.
Ischaemic - Thrombus or atheromatous plaque that blocks a vessel starving a region of brain of oxygen
Haemorrhagic - Subarachnoid or intracranial bleed
What % do Ischaemic strokes account for?
85%
What % do Haemorrhagic strokes account for?
15%
What else can cause a stroke?
Vertebral/carotid dissection (tearing of artery wall)
Space occupying lesion (cancer for eg)
Describe venous blood flow from deep within the brain to the Superior Vena Cava.
Deep cerebral veins > Superficial cerebral veins > Venous sinuses > Internal jugular vein >
Subclavian vein > SVC
What is the blood-CSF barrier?
Separates the CSF and blood
Name the 3 parts of the blood-CSF barrier.
- Choroidal epithelial cells - interconnected by tight junctions and secreting CSF
- Basal membrane
- Endothelium of pia mater capillaries
Describe the layers of the blood-CSF barrier from blood > CSF.
Blood > Endothelium of pia mater capillaries > Basement membrane > choroid cells > CSF
Give 2 features of the choroid cells.
Microvilli to increase surface area
Enzymes to allow active transport of ions and metabolites in and out
Where is the blood-CSF barrier?
In the choroid plexus - which is found in lateral, 3rd and 4th ventricles
What is the cavernous sinus?
A drainage pathway of the brain.
A large collection of thin walled veins creating a cavity
Where does the cavernous sinus receive blood from?
Brain and tributaries of the face
How many cavernous sinuses are there?
2 - one for each hemisphere of the brain
Where is the cavernous sinus?
Base of brain
Bordered by temporal bone and sphenoid bone
What is the mnemonic for remembering what nerves and vessels go through the cavernous sinus?
O TOM CAT
Oculomotor
Trochlear
Ophthalmic trigeminal
Maxillary trigeminal
Carotid (internal)
Abducens
Trochlear
Draw the cavernous sinus.
:)
