The ventricular system Flashcards
How do the ventricles form
- Lumen expands at cranial end to form ventricles
What are the parts of the lateral ventricles that are associated with each lobe
- Anterior horn - frontal lobe
- Body - parietal lobe
- Posterior horn - occipital lobe
- Inferior horn - temporal lobe
What is T1 in CT scans
- Fluid is black, brain tissue appears white - good for looking at structure
What is T2 in CT scans
- Fluid is white, brain tissue appears black - good for looking at fluid
What are the borders of the lateral ventricles
- Septum pellucidum separates lateral ventricles
- Corpus callosum sits in roof
Location of the caudate nucleus
- Sits in lateral wall
Location of the hippocampus
- Hippocampus sits in floor of inferior horn
How do the lateral ventricles communicate with the third ventricle
- Through ventricle through the internventricular foramen AKA foramen of monro
Location of third ventricle
- Slit like cleft between thalami
- Fornix forms roof
What type of matter are corpus callosum, septum pellucidum and fornix
- White matter
What type of matter are caudate nucleus, lentiform nucleus, thalamus and hippocampus
- Gray matter
How does the third ventricle communicate with the 4th ventricle
- Through the cerebral aqueduct AKA aqueduct of sylvius
Location and shape of fourth ventricle
Surrounded by hindbrain
- Cerebellum posterior
- Pons and medulla anterior
- Cerebellar peduncles lateral
- Characteristic peduncles lateral
- Continuous with the central canal of the spinal cord and subarachnoid space
What are the three foramen exits into subarachnoid space
- Two foramen of luschka(lateral)
- One foramen of magendie(middle)
Where do the foramina of luschka and magendie exit into
- Cisterna magna
Role of superior colliculi
- Vision
Role of inferior colliculi
- Hearing
Role of choroid plexus
- CSF production
- Filters blood from branches of internal carotid and basilar arteries
Describe the structure of the choroid plexus -
- Very simple
- Capillary network surrounded by cuboidal epithelium
How is blood filtered by the choroid plexus
- Blood filtered through fenestrated(has holes) capillaries
- Components transported through cuboidal epithelium into ventricles
- There are tight junctions between epithelial cells which prevent macromolecules from entering CSF
- Permeable to water and CO2
- Forms blood-CSF barrier
Describe the cuboidal epithelium in the ventricles
- Specialised ependyma
- Villi present to increase surface area
- Active transport of CSF components
- Bidirectional(uptake of metabolites into circulatory system)
- 60% CSF produced in ventricles
- 40% CSF from other sites within brain
Protein content in CSF in comparison to plasma and why
CSF protein - 0.18 g/l
plasma protein - 75 g/l
- Protein levels low in CSF as the CSF has to be sterile and macromolecules are stopped by tight junctions
What is the cisterna magna
- Is one of the three principal openings in the subarachnoid space between the arachnoid and pia mater layers of the meninges of the brain
What is the subarachnoid space
- Lies between pia and arachnoid
- Subarachnoid space follows contours of brain
Purpose of cSF
Functionally important - CSF in contact with brain parenchyma
- transfer of micronutrients into brain
- removal of metabolites
What are arachnoid granulations
- Herniations of arachnoid membrane(villi) through dura mater into venous sinuses
- Mainly within the superior sagittal and transverse sinuses
Pressure difference between csf and sinuses
- CSF pressure must exceed that in venous sinuses
- 150mm water in subarachnoid space
- 80mm water in venous sinuses
- If venous pressure exceeds CSF pressure, tips of villi close off(prevents reflux of blood into subarachnoid space)
- Arachnoid villi act as one-way valves
How much CSF is produced per day
- 500ml CSF produced per day(0.35ml/min)
What is the total volume of CSF in the system
90-140ml
What happens to excess CSF
- Absorbed by arachnoid granulations
What are the main functions of CSF
- Hydraulic buffer to cushion brain against trauma
- Vehicle for removal of metabolites from CNS
- Stable ionic environment for neuronal function(communicates with brain interstitial fluid via pia)
- Transport for neurotransmitters and chemicals
What does yellow(xanthochromia) CSF indicate?
- Due to conversion of haemoglobin to billirubin
- eg subarachnoid haemorrhage
- lysis of red blood cells, haemoglobin release
What does cloudy CSF indicate?
- Due to presence of lots of antibodies and white blood cells
- eg multiple sclerosis
- Protein content(gamma globulin) increase
- eg bacterial meningitis
- Leukocytes are increased, indicative of infection
How is CSF sampled
- Taken by lumbar puncture at lumbar cistern(no spinal cord)
- L3/4 for adults
- L4/5 for children
- Vertebrae is slower growing than
What is hydrocephalus
- Dilation of brain ventricles
- Due to blocked CSF circulation, impaired absorption or over secretion
- increased intracranial pressure
- Pressure on surrounding tissues affects neurological function
- Can be congenital or acquired
What are the symptoms of hydrocephalus
- Headaches
- Vomiting
- Visual disturbances
- Pailledema(swelling of optic disc)
- Seizures
- Altered cognition
- Balance and coordination problems
What is non-communicating hydrocephalus?
- Blockage within the ventricular system
- Due to tumour, cyst, stenosis(eg narrowing of cerebral aqueduct)
- CSF does not circulate over surface of brain
Normal treatment for non-communicating hydrocephalus
Surgery - insert shunt to reduce intracranial pressure
- Blockage often in the cerebral aqueduct
What is dandy-walker syndrome
- Congenital malformation of the cerebellum
- Obstruction within foramina of fourth ventricle
- Symmetrical dilation of lateral, third and fourth ventricles
Treatment for dandy-walker syndrome
- Insert a shunt to reduce intracranial pressure
- In infancy, child’s head may become enlarged, tend to have a large skull
What is communicating hydrocephalus
- Obstruction in the arachnoid villi
- Movement of CSF into venous is impeded
- eg impaired absorption following subarachnoid haemorrhage trauma or bacterial meningitis
