1. Why is there no true epidural space around the brain? What is located in the
ID: 3518325 • Letter: 1
Question
1. Why is there no true epidural space around the brain? What is located in the subdural and subarachnoid spaces?2. What is the function of CSF and how is it produced?
3. What are the key differences between the cranial and spinal meninges?
4. What types of stimuli do the spinal cord’s ascending tracts carry? What do the spinal cord’s descending tracts carry?
1. Why is there no true epidural space around the brain? What is located in the subdural and subarachnoid spaces?
2. What is the function of CSF and how is it produced?
3. What are the key differences between the cranial and spinal meninges?
4. What types of stimuli do the spinal cord’s ascending tracts carry? What do the spinal cord’s descending tracts carry?
2. What is the function of CSF and how is it produced?
3. What are the key differences between the cranial and spinal meninges?
4. What types of stimuli do the spinal cord’s ascending tracts carry? What do the spinal cord’s descending tracts carry?
Explanation / Answer
1. Why is there no true epidural space around the brain? What is located in the subdural and subarachnoid spaces?
The outer layers are the skin and then a bone layer with associated periosteum. This layer includes the skull and the vertebrae. Below the periosteum is the Epidural Space which lies between periosteum and dura in the vertebral canal. The epidural space contains adipose tissue, loose connective tissue, veins and lymphatics. It cushions the cord as it flexes. The epidural space is regularly used for nerve blocks where a local anaesthetic such as Lidocaine is injected to block signal transmission to and from the spinal cord.
From the fourth ventricle, the cerebrospinal fluid passes into the subarachnoid space where it circulates around the outside of the brain and spinal cord and eventually makes its way to the superior sagittal sinus via the arachnoid granulations also called arachnoid villi. In the superior sagittal sinus, the cerebrospinal fluid is reabsorbed into the blood stream.
The cerebrospinal fluid of the neuraxis is regenerated several times every twenty-four hours.
2. What is the function of CSF and how is it produced?
Cerebrospinal fluid has three main functions:
The cerebrospinal fluid (CSF) is produced from arterial blood by the choroid plexuses of the lateral and fourth ventricles by a combined process of diffusion, pinocytosis and active transfer. A small amount is also produced by ependymal cells.
It is produced in the choroid plexuses of the ventricles of the brain, and absorbed in the arachnoid granulations.
3. What are the key differences between the cranial and spinal meninges?
The dura mater in the brain is fused to the periosteum vs in the spinal cord the epidural space is in between the dura mater and the intervertebral canal. Three fibrous membranes that surround the brain and spinal cord to protect the central nervous system. The pia mater, a very thin membrane, adheres to the surface of the brain and spinal cord. The subarachnoid space, containing cerebrospinal fluid, separates the pia mater from a second membrane, the arachnoid. Around the brain, fine filaments connect these two membranes, which are believed to be impermeable to fluid. The third membrane, the dura mater, is strong, thick, and dense. It envelops the arachnoid, covers the inside of the skull, and surrounds and supports the large venous channels carrying blood from the brain. Several septa divide it and support different parts of the brain. In the spine, the dura mater and the arachnoid mater are separated by the subdural space; the arachnoid and pia mater are separated by the subarachnoid space.
4. What types of stimuli do the spinal cord’s ascending tracts carry? What do the spinal cord’s descending tracts carry?
Ascending tracts are sensory
• Deliver information to the brain
Descending tracts are motor
• Deliver information to the periphery
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