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Let’s start our USMLE Review with Anatomy from the Gold Standard USMLE Step 1 Audio Review program.
Play USMLE Audio MP3 25 07 CSF Summary Below
Begin 25 07 CSF Summary Transcription
Continuing with figure 2.1 we will now consider the cerebrospinal fluid. We will look at the flow of the cerebrospinal fluid in the brain.
Student doctor, what generates the CSF?
- The choroid plexus.
The choroid plexus is located in how many places?
- In four places.
What are these four places where the choroid plexus is located?
- There is a choroids plexus in each lateral ventricles, one in the third ventricle, and one in the fourth ventricle.
Beginning rostrally, where does the cerebrospinal fluid flow first?
- In the lateral ventricles.
And through which foramen does the CSF flow to get from the lateral ventricles to the third ventricle?
- The interventricular foramen of Monro.
Through what structure does the CSF then flow to reach the fourth ventricle?
- The aqueduct of Sylvius.
From the fourth ventricle the CSF may flow into what two spaces?
- Either into the subarachnoid space or further down into the central canal.
The CSF that flows into the subarachnoid space does so via what foramina?
- Via the lateral foramina of Luschka and the medial foramen of Magendie.
Now the CSF in the subarachnoid space encloses and bathes what major parts of the brain?
- All of them. The cerebrum, the thalamus, the midbrain, the brainstem, and the spinal cord.
And in what location is the CSF that is now in the subarachnoid space reabsorbed?
- It is reabsorbed in the cranial cavity surrounding the cerebrum,
particularly in what area?
- The superior dorsal midline of the cranial cavity surrounding the cerebrum.
What are the structures that actually reabsorb the CSF?
- These are the arachnoid villi.
And what structures contain the arachnoid villi?
- These are the arachnoid granulations.
Student doctor, please give a gross description of these arachnoid granulations. Arachnoid granulations are lateral lacunae located alongside the superior sagittal sinus.
Once the CSF is absorbed, where is it, or where does it go?
- Into the venous blood.
Student doctor, please pause and summarize the circulation of cerebrospinal fluid.
The cerebrospinal fluid or CSF is generated by the choroid plexus.
There are four locations for choroid plexus, one in each lateral ventricle, one in the third ventricle, and one in the fourth ventricle. Beginning rostrally,
the CSF flows first in the lateral ventricles.
The CSF then flows from the lateral ventricles to the third ventricle via the interventricular foramen of Monro.
The CSF then flows from the third ventricle to the fourth ventricle via the aqueduct of Sylvius.
From the fourth ventricle the CSF may continue down into the central canal or through foramina into the subarachnoid space.
The CSF may enter the subarachnoid space through the lateral foramina of Luschka or through the medial foramen of Magendie.
In the subarachnoid space the CSF encloses and bathes all the major parts of the brain including the cerebrum, thalamus, midbrain, brainstem, and spinal cord.
The CSF in the subarachnoid space is then reabsorbed in the cranial cavities surrounding the cerebrum, particularly in the superior dorsal midline.
The structures that actually reabsorb the CSF are the arachnoid villi. The arachnoid villi are contained by the arachnoid granulations.
The arachnoid granulations are lateral lacunae located alongside the superior sagittal sinus. Once absorbed, the CSF enters the venous blood.
****END OF TRANSCRIPTION****
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