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19 Cards in this Set

  • Front
  • Back
How is the CNS and the brain set up? What forms the ventricular system?
The CNS contains an interconnecting series of chambers and channels which are derived from the lumen of the embryonic neural tube. In the spinal cord, this is represented by the vestigial central canal.

Within the brain, however, the basic tube-like structure has developed into an elaborate system of ventricles.

The ventricular system consists of the lateral ventricles, third ventricle, cerebral aqueduct and forth ventricle.
Describe the lateral ventricle.
The lateral ventricle is located within the cerebral hemisphere. It is basically a C-shaped structure that circles from the frontal lobe, through the parietal lobe and into the temporal lobe. It also has a short protrusion (posterior horn) into the occipital lobe. It communicates with the third ventricle via the interventricular foramen. The lateral ventricles on each side are separated by the septum pellucidum.
Describe the third ventricle.
The third ventricle is a midline slit-like cavity in the diencephalon. Its lateral walls are bounded by the thalamus and hypothalamus. The third ventricle communicates with the fourth ventricle via the cerebral aqueduct which runs through the midbrain.
Describe the fourth ventricle.
The fourth ventricle is a rhomboid-shaped cavity located between the pons and medulla and the cerebellum. This communicates with the subarachnoid space of the brain via the median aperture and two lateral apertures.
Where is CSF produced?
CSF is produced in the ventricles of the brain by the choroid plexus.
The lateral ventricle communicates with the 3rd ventricle via the...
interventricular foramen.
The lateral ventricles on each side are separated by the...
septum pellucidum.
The third ventricle communicates with the 4th ventricle via the...
cerebral aqueduct.
The fourth ventricle communicates with the subarachnoid space of the brain via the...
median aperture and two lateral apertures.
What is CSF?
CSF is a clear, colourless fluid that fills the ventricles and subarachnoid space. CSF is produced by the choroid plexus in the lateral, third and fourth ventricles. It is formed by a process of active secretion and passive diffusion. It normally contains little protein and few cells.
What is the total volume of CSF in the ventricles and subarachnoid space?
about 140ml and about 25 ml is in the ventricles.
At what rate is CSF produced?
CSF is produced continuously at a rate of about 500ml/day i.e. a rate that would fill the spaces several times a day.
What does the high rate of CSF production mean the body needs?
An effective mechanism is required for the circulation and absorption of CSF.
What happens if the flow or absorption of CSF is blocked?
CSF still continues to be produced within the ventricles. This raises intercranial pressure producing the condition of hydrocephalus. If this pressure is not relieved it can lead to headaches, unsteadiness and mental impairment. Prolonged raised pressure also causes degeneration and loss of nervous tissue.
Describe the development of the choroid plexus.
A blood vessel is located in a layer of pia (closer to vessel) and ependyma.

The blood vessel gets invaginated by the layer of pia and ependyma.

The Choroid plexus in ventricle eventually forms underneath the layer of pia and ependyma.
Describe the flow of CSF.
Lateral ventricle

--> interventricular foramen

--> 3rd ventricle

--> cerebral aqueduct

--> 4th ventricle

--> lateral apperture
--> median aperture
What is another name for the lateral apertures?
Foraminae Luschka
Describe the circulation and absorption of the CSF.
The CSF produced in each of the ventricles, must ultimately flow into the subarachnoid space. From here it circulates around the surface of the CNS, and it is absorbed into the venous sytem of the brain.

CSF flows in the direction: lateral ventricles --> third ventrical via interventricular foramina, third ventricle --> 4th ventricle via the cerebral aqueduct, 4th ventricle to subarachnoid space via the median and lateral apertures.

It is absorbed into the dural superior saggital sinus via the arachnoid villi. The arachnoid villi are tuft-like protrusions of the arachnoid that penetrate the dura and drain CSF into the lumen of the venous sinus, by bulk flow and exocytosis. Clusters of arachnoid villi are known as arachnoid granulations.
What is the main feature of chronic hydocephalus?
Grossly enlarged lateral ventricles and compression and loss of brain tissue.