Class grades 3 Quizzes

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

The Meningesand

the Ventricular System

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.

Protection of the CNS Function:

CNS is fairly soft and gelatinous in nature

Basic protection

Meninges of the Brain

Meninges of the Brain Three Meninges:

The Meninges Bhatnagar & Andy, 1995, Figure 2.45A

Meningeal Layers: Dura Mater Location:

Function:

Meningeal Layers: Dura Mater Structure:

Two spaces

Two fibrous layers of the dura

The Meninges Bhatnagar & Andy, 1995, Figure 2.45A

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

Dural Extensions Falx Cerebri

Location:

Cavity Formations:

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

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

Dural Extensions Tentorium Cerebelli

Location:

Tentorial Notch

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

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

Dural Extensions Falx Cerebelli

Location:

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

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

Meningeal Layers: Arachnoid Membrane Structure:

Location:

Meningeal Layers: Arachnoid Membrane Spaces:

1. Subarachnoid space

2. Subdural space:

The Meninges Bhatnagar & Andy, 1995, Figure 2.45A

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

Meningeal Layers: Pia Mater Location:

Structure:

The Meninges and the Spinal Cord Similar Structures

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

The Ventricles

The Ventricular System Three Parts:

Function:

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

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

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

The Lateral Ventricles Structure and Shape:

Location:

Connection:

Choroid Plexus:

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

The Third Ventricle Location and Shape:

Connection:

Choroid Plexus:

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

The Fourth Ventricle Location:

Shape:

Structure:

Function:

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

Subarachnoid Space Location:

Arachnoid Trabeculae

The Meninges Bhatnagar & Andy, 1995, Figure 2.45A

Ventricles Inner Walls

Cerebrospinal Fluid Structure:

Circulation

Function:

Choroid Plexus Function:

Location:

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

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

Circulation of the CSF Love & Webb,

1996, Figure 3-6

Clinical Considerations Drainage of the CSF

Inadequate Drainage of the CSF

Clinical Considerations Rate of CSF Production

Disassociation between Production and Absorption Rate of the CSF

Clinical Considerations Hydrocephalus

Increased Pressure in the Brain

Sustained Pressure

MRI of Enlarged Lateral Ventricles Secondary to Hydrocephalus

Bhatnagar & Andy, 1995, Figure 18.3

Medical Diagnostic Procedures Measurement of the pressure of the fluid

If abnormally high, may suspect: Intracranial tumor Intracranial hemorrhage Hydrocephalus Meningitis Encephalitis

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

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 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 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

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

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.

The Meningesand

the Ventricular System

Graphics

THINGS TO DO BEFORE LECTURE