Vesicles to Venticles, Blood Supply, and CSF Flashcards
What is the difference between the dura matter in the cranium vs in the spinal column?
The dura matter adheres closely to the inside of the cranium, but hangs loosely within the spinal column.
What is the path of the CNS from its formation to its site of reabsorption?
CNS is produced by the choroid plexus within the lateral ventricles. It flows from the lateral ventricles through the Foramen of Monro into the Third Ventricle and then through the Cerebral Aqueduct (of Sylvius) into the Fourth Ventricle. It then flows through the Foramina of Luschka (2, lateral) or Foramen of Magendie (1, dorsal) into the subarachnoid space throughout the CNS. It is reabsorbed through Arachnoid Granulations and drains into the durable sinuses of the brain.
What are ependymal cells?
Ependymal cells form a single cell layer that lines the ventricles. They have no tight junctions and allow the CSF to freely exchange with the extracellular fluid of the brain.
What is the relationship of ependymal cells and capillaries in the Choroid Plexus?
In the choroid plexus, endothelial cells of the capillaries lose their tight junctions (no astrocyte contact??) and the ependymal cells gain tight junctions. Thus, plasma solutes may freely flow out of the capillaries, but must be actively transported across the ependymal layer to reach the CSF.
How much CSF is produced daily?
500ml of CSF is produced daily by the ependymal cells of the choroid plexus. Only 125ml are present at any one time, so it must be reabsorbed consistently.
What happens to the ionic concentration of CSF as that of blood plasma changes?
The ionic concentration of CSF is very tightly controlled and shows almost no change regardless of blood concentrations. Many neurons of the CNS have their resting membrane potentials very close to the firing threshold, so a change in ECF concentrations could easily induce spontaneous, repetitive firing.
What is a communicating hydrocephalus?
Hydrocephalus occurs when CSF is not reabsorbed at an appropriate rate and builds up within the ventricles or subarachnoid space, compressing the brain. If the CSF flows freely through the ventricles but is not reabsorbed in the subarachnoid space, it is termed a “communicating hydrocephalus”.
What is a non-communicating hydrocephalus?
Hydrocephalus occurs when CSF is not reabsorbed at an appropriate rate and builds up within the ventricles or subarachnoid space, compressing the brain. If the CSF is prevented from flowing through the ventricles by an obstruction of the inter ventricular foramen or cerebral aqueduct, and builds up within the ventricles, it is termed a “non-communicating hydrocephalus”.
