Meninges and ventricular system (Chapters 4, 5)

Question 1

What are the four principle ways in which the brain is supported and protected?

Answer 1

Skull
Meningeal coverings (stabilize shape and position, protect)
Trabechulae (scaffolding to help keep brain suspended in meninges)
CSF (provides buoyancy)

Question 2

What are the “potential” spaces of the meninges and why are they clinically relevant?

Answer 2

• Epidural (between cranium and outer layer of dura)
• Subdural (between innermost dural layers)

Spaces can fill with blood or fluid (epidural - lens shape; subdural - crescent shape, often midline shift)

Question 3

What are the three meningeal layers?

Answer 3

Dura, arachnoid, pia

Question 4

What is a dural reflection or dural fold?

Answer 4

An inner dural layer that separates and protrudes into cranial cavity and folds back on itself, creating brain “compartments”.

Question 5

Name the four major dural reflections.

Answer 5

Falx cerebri (separates cerebral hemispheres)
Falx cerebelli (separates cerebellar hemispheres)
Tentorium cerebelli (between cerebrum and cerebellum)
Diaphragm selli (covers pituitary fossa)

Question 6

Where are sinuses located versus cisterns?

Answer 6

Sinus = between dural layers
Cistern = subarachnoid space (between pia and arachnoid)

Question 7

Name the major sinuses.

Answer 7

Superior sagittal
Inferior sagittal
Confluence
Straight
Transverse
Sigmoid
Cavernous
Occipital
Superior/inferior petrosal

Question 8

Name the major cisterns.

Answer 8

Cisterna magna
Interpeduncular
Chiasmatic
Pontine

Question 9

What is the function of arachnoid villae?

Answer 9

Arachnoid villae extend through the wall of the sinuses, allowing CSF to enter venous circulation. Major site of reabsorption of CSF from the sinuses into the venous system.

Question 10

What is choroid plexus and where is it found?

Answer 10

Choroid plexus is ependymal cells of the ventricle walls that produce CSF. It is found into the atrium of the lateral ventricle, roof of 3rd ventricle, and T-shape in 4th ventricle extending into the median aperture.

Question 11

What are some of the major differences between the spinal and cerebral meninges?

Answer 11

Spinal dura:

• Has no periosteal layer
• Epidural space is real, not potential
• Spinal epidural space is filled with fatty connective tissue

Question 12

What is the function of the 4th ventricle’s medial and lateral apertures?

Answer 12

The three apertures allow the ventricular system to communicate with the subarachnoid space.

Question 13

Describe the route of CSF circulation.

Answer 13

1. Produced by choroid plexus in lateral ventricle
2. Passes through intraventricular foramen (of Monro) to 3rd ventricle
3. Passes through cerebral aqueduct to 4th ventricle
4. Exits into the central spinal canal via median aperture
5. Exits into the cisterna magna and pontine cistern via the lateral apertures
6. From cisterns, flows upward through tentorial notch and is reabsorbed in the superior sagittal sinus

Question 14

What is communicating vs. noncommunicating hydrocephalus?

Answer 14

Communicating = connection to subarachnoid space is blocked
Noncommunicating = blockage of connections in the ventricular system (i.e., 3rd ventricle cyst)