L12. Ventricular system (AD) Flashcards
give an overview of the ventricular system
- Series of CSF-filled interconnected spaces
- Continuous with the subarachnoid space and central canal
how do the ventricles develop (embryonic stage )
- Neuroectoderm forms neural tube
- Lumen of neural tube becomes ventricles and central canal
- Ependymal layer lines ventricles and central canal
describe the lateral ventricles
- Two ventricles – Very large
One for each cerebral hemisphere
Body, anterior, posterior and inferior horn
corresponding to lobes of the hemisphere
look at labelling for lateral ventricles in slide 6
how was it
what are the borders of the lateral ventricles
- Septum pellucidum separates lateral ventricles
- Corpus callosum sits in roof
- Caudate nucleus sits in lateral wall
- Hippocampus sits in floor of inferior horn
slide 9
describe the interventricular foramen
Lateral ventricles communicate with the third ventricle through the interventricular foramen
- Also called Foramen of Monro
describe the third ventricle
- cleft between thalami
- fornix forms roof
study slide 12
how was it
describe the cerebral aqueduct
- Third ventricle communicates with fourth ventricle through the cerebral aqueduct
- Also called Aqueduct of Sylvius
– Surrounded by the midbrain
describe the 4th ventricle
Surrounded by hindbrain:
- Cerebellum posterior
- Pons and medulla anterior
- Cerebellar peduncles lateral
Characteristic rhomboid shape (coronal view)
Continuous with the central canal of the spinal cord and subarachnoid space
describe 4th ventricle communication
Three foramen exit into subarachnoid space:
- Two Foramen of Luschka (lateral)
- One Foramen of Magendie (middle)
- Into Cisterna Magna
study slide 17
how was it
describe the choroid plexus
CSF produced by choroid plexus
Filters blood from branches of internal carotid and basilar arteries
Choroid plexus present throughout ventricles:
describe the structure of the choroid plexus
Very simple
Capillary network surrounded by cuboidal epithelium
During CSF production:
1. Blood filtered through fenestrated capillaries 2. Components transported through cuboidal epithelium into ventricles
3) Tight junctions between epithelial cells
- Prevent macromolecules from entering CSF
- Permeable to water and CO2
4)- Forms blood-CSF barrier
study slide 20
how was it
describe the cuboidal epithelium
Specialized ependyma
Villi present to increase surface area
Active transport of CSF components
Bidirectional (uptake of metabolites into circulatory system)
give the estimate % of CSF production in the head
60% CSF produced in ventricles
40% CSF from other sites within brain
what is the CSF composition ideal for
physiological functioning of neurons
what are the differences in protein composition between CSF and Plasma
CSF- 0.18g/l
Plasma- 75g/l
Differences due to regulation by active transport
describe the route of CSF circulation
Lateral ventricles
(Interventricular foramen)
Third ventricle
(Cerebral aqueduct
)
Fourth ventricle
(Luschka and Magendie
foramina)
Cisterna magna
(subarachnoid space)
CSF passes out of ventricles into the subarachnoid space
then up spinal
subarachnoid space
Over cerebral hemispheres
(including arachnoid granulations & superior sagittal sinus)
then down dorsal spinal subarachnoid space
(central canal usually blocked in adults)
slides 23-24
describe the subarachnoid space
Lies between pia and arachnoid
Subarachnoid space follows contours of brain
Functionally important: CSF in contact with brain parenchyma
- transfer of micronutrients into brain - removal of metabolites
describe the arachnoid granulations
Herniations of arachnoid membrane (villi) through dura mater into venous sinuses
Mainly within the superior sagittal and transverse sinuses
describe the absorption of CSF
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
describe CSF volume and its factors
500ml CSF produced per day (0.35ml/min)
Total volume in system = 90-140ml
- Normally quoted 140ml
30 ml ventricles
110ml subarachnoid space
Continuously moving
Excess absorbed by arachnoid granulations
what is 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 of neurotransmitters and chemicals
describe the different colours of CSF in disease
CSF normally clear sterile fluid
Discoloured in some pathological states:
Yellow (Xanthocromia)
E.g. Subarachnoid haemorrhage
- Lysis of red blood cells, haemoglobin release
Cloudy
E.g. Multiple sclerosis
- Protein content (gamma globulin) increase
E.g. Bacterial meningitis
- Leukocytes are increased, indicative of infection
how is CSF sampled
Taken by lumbar puncture
At lumbar cistern
- No spinal cord
describe the condition 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
– Symptoms include: headaches, vomiting, visual disturbances, papilledema (swelling of optic disc), seizures, altered cognition, balance and coordination problems
describe non-communicating hydrocephalus
Blockage within the ventricular system
- Due to tumour, cyst, stenosis (e.g. narrowing of cerebral aqueduct)
CSF does not circulate over surface of brain
Surgery: Insert shunt to reduce intracranial pressure
describe Dandy-walker syndrome
Congenital malformation of the cerebellum (1:30,000 births)
Obstruction within foramina of fourth ventricle:
-Symmetrical dilation of lateral, third and fourth ventricles
In infancy, child’s head may become enlarged:
describe communicating hydrocephalus
Obstruction in the arachnoid villi
Movement of CSF into venous sinuses is impeded
- E.g. Impaired absorption following subarachnoid haemorrhage, trauma or bacterial meningitis
