Ventricular system and CSF Flashcards
Ventricle development
- Time
- Structure
Occurs at embryological Day 24
Ventricles and central canal arises from neural tube lumen.
Ependymal layer of neural tube- lines ventricle and central canal
Telencephalon—-> Lateral ventricles.
Diencephalon—-> Third ventricle.
Mesencephalon—-> Cerebral aqueduct.
Metencephalon—-> Fourth ventricle.
Lateral ventricles
- Origin in development
- Structure
- Foramen
Largest ventricles- from telencephalon
Two spaces in each cerebral hemispheres
- Separated by septum pellucidum
Divided by horns:
- Anterior [Frontal lobe]
- Body [parietal lobe]
- Posterior [Occipital lobe]
- Inferior [ Temporal lobe]
Foramen into third ventricle:
Foramen of Monro/ Interventricular foramen
Borders of lateral ventricles
Lateral wall
- Caudate nucleus
Floor of inferior horn
- Hippocampus
Roof
- Corpus callosum
Third ventricle
- Origin in development
- Structure
- Foramen
Developed from diencephalon- surrounded by the midbrain
Central cleft like structure, between thalami.
Foramen to fourth ventricle
- Cerebral aqueduct/ Aqueduct of Sylvius
Third ventricle anatomical borders
Fornix= root
Thalami- lateral wall
Fourth ventricle
- Origin in development
- Structure
- Foramen
Developed from metencephalon
Rhomboid shape [coronal]
3 foramens into cisterna magna [subarachnoid space] :
1x Foramen of Magendie [middle]
2x Foramen of Lushka [lateral]
Fourth ventricle anatomical borders
Cerebellum- posterior
Pons + medulla- anterior
Cerebellar peduncles- lateral
Circulation of CSF from lateral ventricles to cisterna magna
Lateral ventricles —–[Foramen of Monro]– >
Third ventricles —-[Cerebral aqueduct]–>
Fourth ventricle—[Formen of Lushka/ Mangedie]–> Cisterna magna
Circulation of CSF from cisterna magna to the superior sagittal sinus.
- [posteriorly] Cisterna magna —> Over cerebellum + cerebral hemispheres –>
arachnoid granulations—>
Superior sagittal sinus
- [anteriorly] Cisterna magna —> Down dorsal spinal
subarachnoid space—>
Up ventral spinal subarachanoid space–>
Over cerebral hemisphere–>
Arachnoid granulations –>
superior sagittal sinus
Function of subarachnoid space
Allows diffusion of metabolites from and to pia.
CSF composition
Contains very few cells and very low protein levels
- Caused by filtration of choroid plexus
Higher Cl- than plasma
Lower K+ and Ca2+ than plasma
CSF function
Hydraulic buffer
- Cushions brain—> protects from trauma
Removes CNS metabolites
Creates stable ionic environment for neuronal function.
Transporter for NT and chemicals
CSF absorption
Pressure in CSF must exceed pressure in venous sinuses in order for CSF to be absorbed
CSF pressure= 150mm
Venous pressure= 80 mm
Villi on cuboidal epithelial cells have one way valve to prevent flow of blood into subarachnoid space.
Lumbar puncture
Method of sampling CSF from the spine at lumbar cistern.
Taken from L3/4 in adults but L4/5 in children [ spinal cord grows quicker than skeleton].
Choroid plexus
- Structure
- Mechanism
- Function
Produces CSF by filtering arterial blood from ICA and basilar artery.
Structure + mechanism:
- Fenestrated capillaries [allows filtration of small molecules].
- Specialised ependymal cuboidal epithelium, with tight junctions + villi [actively transports CSF content bidirectionally]
- Tight junctions: between cuboidal cells, only permeable to CO2 and water. Forms blood-CSF barrier.
