3 major components of the skull:
Brain 85%
Blood 7%
CSF 7%
All 3 components contribute to X
What do changes in X reflect?
Contribute to intracranial pressure
*ICP is generally measured as CSF pressure
Changes in ICP reflect changes in the volume of the intracranial contents
Total volume of CSF, how much is located where?
150ml
25ml - located in the ventricles (lateral, third, fourth) and spinal central canal
125ml - surrounds brain and spinal cord in the sub-arachnoid space (b/w arachnoid mater and pia mater)
CSF is formed at a rate of ______
500ml/day
Where is CSF produced?
80% produced by ependymal cells in the choroid plexus
- choroid plexus is a network of blood vessels in each cerebral ventricle of the brain
- ependymal cells are columnar cells that line the fluid-filled spaces in the brain and spinal cord
The rest is secreted in interstitial spaces of the brain
Central canal
Central canal is lined by a single layer of columnar ependymal epithelial cells, and transports CSF from brain’s ventricular system to the spinal cord
CSF flow
CSF flows form the lateral ventricle => 3rd ventricle => via cerebral aqueduct to the 4th ventricle => bathe whole brain and spinal cord
How is CSF reabsorbed into the venous circulation?
Reabsorbed through arachnoid granulation and dural sinus
- Arachnoid granulation (pouch like arising from arachnoid membrane from subarachnoid space) allows CSF to exit subarachnoid space and enter the bloodstream
- (IC1): CSF is absorbed into the superior sagittal sinus by arachnoid granulations
- Dural sinus is located in the dura mater, it drains venous blood circulating from the cranial cavity
Functions of CSF
(4 main functions)
- Shock absorber to protect brain
- Clear waste (since brain has no lymphatic channels)
- Distribution of material via CSF
- Creates buoyancy of the brain - decrease brain weight/load
