1. Class grades 3 Quizzes Clinical Notebooks Due: 2 Exams
9/27: Ventricular System
11/20: Brainstem and Basal Ganglia
12/6: Cranial Nerves
Clinical Notebooks Due:
11/13----no late submissions accepted
2 Exams
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

2. The Meninges and the Ventricular System

3. Learning Objectives
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.
Learning Objectives
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.

4. Protection of the CNS Function:
CNS is fairly soft and gelatinous in nature
Basic protection
Protection of the CNS
Function:
CNS is fairly soft and gelatinous in nature
Make the brain and spinal cord susceptible to traumatic injuries
Basic protection
1. Three meningeal layers
2. Cushioning cerebrospinal fluid
3. Bony wall of the skull and the vertebral column

5. Meninges of the Brain

6. Meninges of the Brain Three Meninges: Meninges of the Brain
Consist of concentric fibrous tissue membranes that encase the CNS
1. Dura mater
2. Arachnoid membrane
3. Pia mater

7. The Meninges Bhatnagar & Andy, 1995, Figure 2.45A The Meninges

8. Meningeal Layers: Dura Mater
Location:
Function:
Meningeal Layers: Dura Mater
Location:
Gray outermost membrane
Attached to inner surface of the skull
Overlies the arachnoid membrane
Function:
Provides the maximum meningeal protection of the CNS

9. Meningeal Layers: Dura Mater
Structure:
Two spaces
Two fibrous layers of the dura
Meningeal Layers: Dura Mater
Structure:
Consists of dense, fibrous, connective tissues
Two spaces
1. Epidural
The potential space between the dura and the bone
2. Subdural
The potential space between the dura mater and the arachnoid
Two fibrous layers of the dura
Attached to each other
Except to form sinuses
That absorb blood from veins and the circulated cerebrospinal fluid
1. Periosteal: External layer
Attached to the inner surface of the cranium
2. Meningeal: Internal layer
Forms various septa (dural extensions)
Forms two lateral compartments for the cerebral hemispheres
And one posterior compartment for the cerebellum

10. The Meninges Bhatnagar & Andy, 1995, Figure 2.45A The Meninges

11. The Meninges Love & Webb, 1996, Figure 3-3 The Meninges

12. Dural Extensions Falx Cerebri Location: Cavity Formations:
The largest dural reflection
Location:
Extends longitudinally in the interhemispheric fissure
Between the two hemispheres
Forms a vertical partition in the cranial cavity between two cerebral hemispheres
Cavity Formations:
Dorsal edge of the interhemispheric fissure
Forms the cavity for the Superior Sagittal Sinus
Inferiorly within this fissure above the corpus callosum
Inferior Sagittal Sinus is along the free inferior margin of the falx cerebri

13. Dural Extensions on Midsagittal Section
Bhatnagar & Andy, 1995, Figure 2.43
Dural Extensions on Midsagittal Section
Bhatnagar & Andy, 1995, Figure 2.43

14. Dural Extensions on Coronal View
Bhatnagar & Andy, 1995, Figure 2.44A
Dural Extensions on Coronal View
Bhatnagar & Andy, 1995, Figure 2.44A

15. Dural Extensions Tentorium Cerebelli Location: Tentorial Notch
Arises from the petrous portion of the temporal bone
Margins are inserted between the cerebellum and the basal surface of the temporal and occipital lobes
Occipital lobes lie over it
Cerebellum located below it
Tentorial Notch
Anteriorly, free borders of the tentorium cerebelli
Constitute the Tentorial notch
Opening
Where the brainstem descends through the tentorial notch toward the foramen magnum

16. Dural Extensions on Midsagittal Section
Bhatnagar & Andy, 1995, Figure 2.43
Dural Extensions on Midsagittal Section
Bhatnagar & Andy, 1995, Figure 2.43

17. Dural Extensions on Coronal View
Bhatnagar & Andy, 1995, Figure 2.44A
Dural Extensions on Coronal View
Bhatnagar & Andy, 1995, Figure 2.44A

18. Dural Extensions Falx Cerebelli Location: Dural Extensions
Extension from the tentorial cerebelli
Separates the two cerebellar hemispheres

19. Dural Extensions on Midsagittal Section
Bhatnagar & Andy, 1995, Figure 2.43
Dural Extensions on Midsagittal Section
Bhatnagar & Andy, 1995, Figure 2.43

20. Dural Extensions on Coronal View
Bhatnagar & Andy, 1995, Figure 2.44A
Dural Extensions on Coronal View
Bhatnagar & Andy, 1995, Figure 2.44A

21. Meningeal Layers: Arachnoid Membrane
Structure:
Location:
Meningeal Layers: Arachnoid Membrane
Structure:
Thin, nonvascular membrane
Location:
Between the internal pia mater and the external dura mater
Does not adhere to the cortical surfaces like the pia mater

22. Meningeal Layers: Arachnoid Membrane
Spaces:
1. Subarachnoid space
2. Subdural space:
Meningeal Layers: Arachnoid Membrane
Spaces:
Space between the pia and the arachnoid
Traversed by Arachnoid Trabeculae
Consist of fibrous and elastic connective tissue
1. Subarachnoid space
Between the arachnoid and the pia
Filled with cerebrospinal fluid
Produced in the ventricular system
Enters the subarachnoid space through openings in the fourth ventricle
Subarachnoid space envelopes the entire nervous system
2. Subdural space: Space between the dura mater and the arachnoid
Arachnoid granulations (villi)
Push through the dura
Cerebrospinal fluid drains through villi into the vascular system

23. The Meninges Bhatnagar & Andy, 1995, Figure 2.45A The Meninges

24. Arachnoid Villi or Granulations
Bhatnagar & Andy, 1995, Figure 2.41
Arachnoid Villi or Granulations
Bhatnagar & Andy, 1995, Figure 2.41

25. Meningeal Layers: Pia Mater
Location:
Structure:
Meningeal Layers: Pia Mater
Location:
Closely attached to the surface of the brain
Follows the contours of the gyri and sulci
Structure:
Thin, transparent, collagenous (connective tissue) membrane
Contains a network of blood vessels
That penetrates the pia before entering the cortical substance
Pia also surrounds the blood vessels
Forms a perivascular space

26. The Meninges and the Spinal Cord
Similar Structures
The Meninges and the Spinal Cord
Similar structure as the meninges in the brain
With a few exceptions
Dura is single-layered instead of two layers

27. The Spinal Cord and Its Meninges
Bhatnagar & Andy, 1995, Figure 2.46
The Spinal Cord and Its Meninges
Bhatnagar & Andy, 1995, Figure 2.46

28. The Ventricles

29. The Ventricular System
Three Parts:
Function:
Three Parts:
1. The Lateral Ventricles
2. The Third Ventricle
3. The Fourth Ventricle
Function:
Serves as a pathway for the circulation of the CSF
Each ventricle contains a tuft-like structure called the Choroid Plexus
*Which is concerned mainly with the production of CSF

30. Ventricular System in Relation to Brain: Lateral View
Bhatnagar & Andy, 1995, Figure 2.37
Ventricular System in Relation to Brain: Lateral View
Bhatnagar & Andy, 1995, Figure 2.37

31. Ventricular System: Lateral View
Bhatnagar & Andy, 1995, Figure 2.35A
Ventricular System: Lateral View
Bhatnagar & Andy, 1995, Figure 2.35A

32. Ventricular System: Dorsal View
Bhatnagar & Andy, 1995, Figure 2.35B
Ventricular System: Dorsal View
Bhatnagar & Andy, 1995, Figure 2.35B

33. The Lateral Ventricles
Structure and Shape:
Location:
Connection:
Choroid Plexus:
The Lateral Ventricles
Structure and Shape:
Paired, one in each hemisphere
C-shaped cavity
Location:
In the parietal lobe, and anterior, posterior and inferior horns, extending into the frontal, occipital, and temporal lobes, respectively
Connection:
Connected to the third ventricle by an opening called the intraventricular foramen or the foramen of Munro
Choroid Plexus:
Projects into the cavity on its medial aspect

34. Ventricular System in Relation to Brain: Lateral View
Bhatnagar & Andy, 1995, Figure 2.37
Ventricular System in Relation to Brain: Lateral View
Bhatnagar & Andy, 1995, Figure 2.37

35. The Third Ventricle Location and Shape: Connection: Choroid Plexus:
Small slit between the thalami
Connection:
Connected to the third ventricle by an opening called the intraventricular foramen or the foramen of Munro
Connected also to the fourth ventricle, through the cerebral aqueduct of the aqueduct of Sylvius
Choroid Plexus:
Situated above the roof of the ventricle

36. Ventricular System in Relation to Brain: Lateral View
Bhatnagar & Andy, 1995, Figure 2.37
Ventricular System in Relation to Brain: Lateral View
Bhatnagar & Andy, 1995, Figure 2.37

37. The Fourth Ventricle Location: Shape: Structure: Function: Location:
Anterior to the cerebellum and posterior to the pons and the superior half of the medulla
Continuous superiorly with the cerebral aqueduct and the central canal below
Shape:
Tent-shaped roof, two lateral walls, and a floor
Structure:
Three small openings
The two lateral foramina of Luschkea
The median foramen of Magendie
Function: CSF enters the subarachnoid through these openings

38. Ventricular System in Relation to Brain: Lateral View
Bhatnagar & Andy, 1995, Figure 2.37
Ventricular System in Relation to Brain: Lateral View
Bhatnagar & Andy, 1995, Figure 2.37

39. Subarachnoid Space Location: Arachnoid Trabeculae Subarachnoid Space
Located around the entire CNS
Between the arachnoid membrane and the pia mater
Arachnoid Trabeculae
Extend from the arachnoid to pia mater
Contribute to the maintenance of the subarachnoid space
Which is filled with CSF

40. The Meninges Bhatnagar & Andy, 1995, Figure 2.45A The Meninges

41. Ventricles Inner Walls Ventricles Inner Walls
Lined with a layer of the Ependymal Cells
Glia cells
Prevent infusion of external substances into the cerebrospinal fluid

42. Cerebrospinal Fluid Structure: Circulation Function: Structure:
Clear, colorless fluid that suspends the brain and the spinal cord
Circulation
Circulates from the ventricles to the subarachnoid space
Function:
Serves as a cushion between the CNS and the surrounding bones
*Thereby protecting the brain and spinal cord against direct trauma
Fluid aids in:
Regulation of intracranial pressure
Nourishment of the nervous tissue
Removal of waste products

43. Choroid Plexus Function: Location: Function: Produces CSF Location:
Primarily in the center of the lateral and fourth ventricles

44. Path of CSF Circulation
Pathway:
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
Pathway:
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

45. The Ventricular System: Midsagittal View
Bhatnagar & Andy, 1995, Figure 18.2
The Ventricular System: Midsagittal View
Bhatnagar & Andy, 1995, Figure 18.2

46. Circulation of the CSF Love & Webb, 1996, Figure 3-6

47. Clinical Considerations
Drainage of the CSF
Inadequate Drainage of the CSF
Clinical Considerations
Drainage of the CSF
Draining of the CSF from the subarachnoid space
Is a pressure sensitive process
Emptying of CSF into the Superior Sagittal Sinus
Requires a pressure differential between the subarachnoid space and the venous-sinus system
*At least mmH20 regulates normal CSF drainage from the arachnoid villi
Inadequate Drainage of the CSF
If for any reason, this pressure differential is altered
And the sinus pressure exceeds the ventricular pressure
The one-way openings of the arachnoid villi close
Ending the draining and elevating intracranial pressure

48. Clinical Considerations
Rate of CSF Production
Disassociation between Production and Absorption Rate of the CSF
Clinical Considerations
Rate of CSF Production
Is independent of its absorption and interventricular pressure
CSF continues to be produced
Even after an interruption in its drainage into the sinus system
Disassociation between Production and Absorption Rate of the CSF
Results in hydrocephalus
Three contributing etiologies:
1. Increased production of CSF
2. Blocking of draining passage
Through which the CSF reaches the subarachnoid space
3. Impaired absorption of the CSF

49. Clinical Considerations
Hydrocephalus
Increased Pressure in the Brain
Sustained Pressure
Clinical Considerations
Hydrocephalus
Increased Pressure in the Brain
Regardless of the underlying cause
An excessive amount of CSF pressure
Results in an increased pressure in the brain
Sustained Pressure
Causes enlargement of the ventricles
Compresses the surrounding white and gray matters
Results in damage to the surrounding vital cortical tissues
If hydrocephalus occurs in infancy
The increased CSF pressure
Also causes an enlargement of the cranial vault

50. MRI of Enlarged Lateral Ventricles Secondary to Hydrocephalus
Bhatnagar & Andy, 1995, Figure 18.3
MRI of Enlarged Lateral Ventricles Secondary to Hydrocephalus
Bhatnagar & Andy, 1995, Figure 18.3

51. Medical Diagnostic Procedures
Measurement of the pressure of the fluid
If abnormally high, may suspect:
Intracranial tumor
Intracranial hemorrhage
Hydrocephalus
Meningitis
Encephalitis
Measurement of the pressure of the fluid
If abnormally high, may suspect:
Intracranial tumor
Intracranial hemorrhage
Hydrocephalus
Meningitis
Encephalitis
*Sustained pressure causes enlargement of the ventricles and damage to the surrounding vital cortical tissues
Due to compression of the surrounding white and gray matters

52. Treatment Hydrocephalus No longer a fatal condition If diagnosed early
Can be surgically treated
Treatment
Involves diverting the blocked ventricular CSF
To another cavity for absorption
Procedure
Tube is surgically inserted in the ventricular cavity
And use to divert CSF flow to the peritoneal cavity in the abdomen
Treatment
Hydrocephalus
No longer a fatal condition
If diagnosed early
Can be surgically treated
Involves diverting the blocked ventricular CSF
To another cavity for absorption
Procedure:
Tube is surgically inserted in the ventricular cavity
And used to divert CSF flow to the peritoneal cavity in the abdomen

53. Medical Diagnostic Procedures
Lumbar Puncture or Spinal Tap
Needle inserted into the lumbar subarachnoid space
Between the fourth and fifth lumbar vertebrae
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
Lumbar Puncture or Spinal Tap
Needle inserted into the lumbar subarachnoid space
Between the fourth and fifth lumbar vertebrae
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

54. Medical Diagnostic Procedures
Catheter Insertion into the Lateral Ventricles
Measure Ventricular pressure
Increased intracranial pressure occurs in response to:
1. Increased amounts of CSF
2. Brain swelling
3. And brain tumors
Medical Diagnostic Procedures
Catheter Insertion into the Lateral Ventricles
Measure Ventricular pressure
Increased intracranial pressure occurs in response to:
1. Increased amounts of CSF
2. Brain swelling
3. And brain tumors

55. Medical Diagnostic Procedures
Additional Procedures Associated with Spinal Puncture
Procedure also used to draw out CSF for chemical or cell studies
Diseases of the CNS change the constituent composition of the CSF
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
From the lower body up to the level of the spinal injection
Medical Diagnostic Procedures
Additional Procedures Associated with Spinal Puncture
Procedure also used to draw out CSF for chemical or cell studies
*Diseases of the CNS change the constituent composition of the CSF
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
From the lower body up to the level of the spinal injection

56. Define the Following Technical Terms:
Arachnoid granulations
Arachnoid trabecula
Cerebrospinal fluid
Choroid plexus
Ependymal cells
Intracranial pressure
Lumbar Puncture
Meninges
Meningitis
Septum
Subarachnoid space
Subdural space
Ventricles
Define the Following Technical Terms:
Arachnoid granulations
Arachnoid trabecula
Cerebrospinal fluid
Choroid plexus
Ependymal cells
Intracranial pressure
Lumbar Puncture
Meninges
Meningitis
Septum
Subarachnoid space
Subdural space
Ventricles

57. Review Questions
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.
Review Questions
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.

58. The Meninges and the Ventricular System
Graphics
Graphics:
57,30,31,29,23,12,13,9,26,44,49,10,45

59. THINGS TO DO BEFORE LECTURE