Transcript Protection and Nourishment of the Brain

Class grades
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3 Quizzes
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9/27: Ventricular System
11/20: Brainstem and
Basal Ganglia
12/6: Cranial Nerves
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2 Exams
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Clinical Notebooks
Due:
11/13----no late
submissions accepted
11/1: Somatosensory
System, Visual System,
Central Auditory System,
and Vestibular System
11/27: Motor System:
Cortical Level,
Cerebellum, Brainstem,
Basal Ganglia and Spinal
Cord
The Meninges
and
the Ventricular System
Learning Objectives
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1. Describe the meninges, their locations, and their
functions.
2. Identify parts of the ventricular cavities.
3. Discuss functions of cerebrospinal fluid.
4. Describe the mechanism of cerebrospinal fluid
production.
5. Describe the circulation of cerebrospinal fluid.
6. Explain the diagnostic significance of the
cerebrospinal fluid.
Protection of the CNS
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Function:
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CNS is fairly soft and gelatinous in nature
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Basic protection
Meninges of the Brain
Meninges of the Brain
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Three Meninges:
The Meninges
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Bhatnagar & Andy, 1995, Figure 2.45A
Meningeal Layers: Dura
Mater
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Location:
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Function:
Meningeal Layers: Dura
Mater
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Structure:
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Two spaces
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Two fibrous layers of the dura
The Meninges
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Bhatnagar & Andy, 1995, Figure 2.45A
The Meninges
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Love & Webb, 1996, Figure 3-3
Dural Extensions
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Falx Cerebri
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Location:
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Cavity Formations:
Dural Extensions on
Midsagittal Section
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Bhatnagar & Andy, 1995, Figure 2.43
Dural Extensions on Coronal
View
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Bhatnagar & Andy, 1995, Figure 2.44A
Dural Extensions
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Tentorium Cerebelli
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Location:
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Tentorial Notch
Dural Extensions on
Midsagittal Section
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Bhatnagar & Andy, 1995, Figure 2.43
Dural Extensions on Coronal
View
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Bhatnagar & Andy, 1995, Figure 2.44A
Dural Extensions
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Falx Cerebelli
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Location:
Dural Extensions on
Midsagittal Section
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Bhatnagar & Andy, 1995, Figure 2.43
Dural Extensions on Coronal
View
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Bhatnagar & Andy, 1995, Figure 2.44A
Meningeal Layers: Arachnoid
Membrane
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Structure:
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Location:
Meningeal Layers: Arachnoid
Membrane
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Spaces:
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1. Subarachnoid space
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2. Subdural space:
The Meninges
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Bhatnagar & Andy, 1995, Figure 2.45A
Arachnoid Villi or Granulations
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Bhatnagar & Andy, 1995, Figure 2.41
Meningeal Layers: Pia Mater
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Location:
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Structure:
The Meninges and the Spinal
Cord
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Similar Structures
The Spinal Cord and Its
Meninges
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Bhatnagar & Andy, 1995, Figure 2.46
The Ventricles
The Ventricular System
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Three Parts:
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Function:
Ventricular System in Relation
to Brain: Lateral View
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Bhatnagar & Andy, 1995, Figure 2.37
Ventricular System: Lateral
View
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Bhatnagar & Andy, 1995, Figure 2.35A
Ventricular System: Dorsal
View
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Bhatnagar & Andy, 1995, Figure 2.35B
The Lateral Ventricles
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Structure and Shape:
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Location:
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Connection:
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Choroid Plexus:
Ventricular System in Relation
to Brain: Lateral View
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Bhatnagar & Andy, 1995, Figure 2.37
The Third Ventricle
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Location and Shape:
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Connection:
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Choroid Plexus:
Ventricular System in Relation
to Brain: Lateral View
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Bhatnagar & Andy, 1995, Figure 2.37
The Fourth Ventricle
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Location:
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Shape:
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Structure:
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Function:
Ventricular System in Relation
to Brain: Lateral View
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Bhatnagar & Andy, 1995, Figure 2.37
Subarachnoid Space
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Location:
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Arachnoid Trabeculae
The Meninges
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Bhatnagar & Andy, 1995, Figure 2.45A
Ventricles
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Inner Walls
Cerebrospinal Fluid
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Structure:
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Circulation
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Function:
Choroid Plexus
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Function:
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Location:
Path of CSF Circulation
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Pathway:
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Flows from the lateral ventricles into the third ventricle
 Via Monro’s foramen
Then flows from the third ventricle to the fourth ventricle
through the cerebral aqueduct
Then flows from the fourth ventricle into the subarachnoid
space through three apertures
 Two lateral Foramina of Luschka
 One mediodorsal Magendie’s foramen
Then travels to reach the inferior surface of the cerebrum
and moves superiorly over the lateral aspect of each
hemisphere
Some of it moves into the subarachnoid space around the
spinal cord
The Ventricular System:
Midsagittal View
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Bhatnagar & Andy, 1995, Figure 18.2
Circulation of the CSF
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Love & Webb,
1996,
Figure 3-6
Clinical Considerations
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Drainage of the CSF
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Inadequate Drainage of the CSF
Clinical Considerations
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Rate of CSF Production
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Disassociation between Production and
Absorption Rate of the CSF
Clinical Considerations
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Hydrocephalus
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Increased Pressure in the Brain
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Sustained Pressure
MRI of Enlarged Lateral Ventricles
Secondary to Hydrocephalus
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Bhatnagar & Andy, 1995, Figure 18.3
Medical Diagnostic
Procedures
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Measurement of the pressure of the fluid
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If abnormally high, may suspect:
 Intracranial tumor
 Intracranial hemorrhage
 Hydrocephalus
 Meningitis
 Encephalitis
Treatment
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Hydrocephalus
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No longer a fatal condition
 If diagnosed early
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Can be surgically treated
Treatment
 Involves diverting the blocked ventricular CSF
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To another cavity for absorption
Procedure
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Tube is surgically inserted in the ventricular cavity
 And use to divert CSF flow to the peritoneal
cavity in the abdomen
Medical Diagnostic
Procedures
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Lumbar Puncture or Spinal Tap
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Needle inserted into the lumbar subarachnoid
space
 Between the fourth and fifth lumbar vertebrae
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Because spinal penetration at this point does not
cause any injury to nerve fibers
Attach needle hub to a manometer or other
pressure sensitive device
 A pressure level higher than normal suggests
that a pathologic process exists
Medical Diagnostic
Procedures
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Catheter Insertion into the Lateral Ventricles
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Measure Ventricular pressure
 Increased intracranial pressure occurs in
response to:
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1. Increased amounts of CSF
2. Brain swelling
3. And brain tumors
Medical Diagnostic
Procedures
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Additional Procedures Associated with Spinal
Puncture
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Procedure also used to draw out CSF for chemical or cell
studies
 Diseases of the CNS change the constituent composition
of the CSF
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An alteration serves as a diagnostic tool for identifying
pathologic changes that occur in the brain and spinal cord
 May suggest acute bacterial meningitis
Route used to inject drugs to combat infection or to induce
anesthesia
 Anesthesia prevents nerve impulses from being
conducted through the spinal nerves
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From the lower body up to the level of the spinal injection
Define the Following Technical
Terms:
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Arachnoid granulations
Arachnoid trabecula
Cerebrospinal fluid
Choroid plexus
Ependymal cells
Intracranial pressure
Lumbar Puncture
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Meninges
Meningitis
Septum
Subarachnoid space
Subdural space
Ventricles
Review Questions
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1. Discuss the function of the meningeal membranes
of the brain and spinal cord.
2. Describe the location of epidural, subdural, and
arachnoid spaces.
3. Name the dural extensions of the brain and
describe their relationship to the brain.
4. With a labeled diagram, identify major parts of the
ventricular system.
5. Discuss the functions of the cerebrospinal fluid.
6. Discuss the production, circulation, and absorption
of the cerebrospinal fluid.
7. Describe the mechanism, clinical implications, and
treatment of hydrocephalus.
The Meninges
and
the Ventricular System
Graphics
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