Meningeal Coverings of CNS

Question 1

What are 2 functions of the Meninges

What are the 2 ways it functions?

Answer 1

To support the shape of the CNS
To provide a cushioning suspension

Mechanically suspends brain to the skull
Buoyancy of CSF to reduce effective weight to 1/30th of what it is in the air.

Question 2

Describe 3 things about the Dura Mater

Answer 2

It is the thickest and toughest collagenous membrane layer.
The outermost membrane layer.
Composed of 2 layers–Periosteum; connected to skull.
Meningeal dura; connected to the brain.

Question 3

The arachnoid layer is attached to which? Dura mater or Pia mater?
How does Arachnoid Mater get its name?

Answer 3

Dura Mater.

few cell layers, interspersed bundles of collagen in a spider-web like pattern.

Question 4

What is Arachnoid Trabeculae? What is its function?

Answer 4

Loosely connects arachnoid layer with the pia mater.

Functions as flexible suspension for the brain in the subarachnoid space.

Question 5

What is the relationship between Arachnoid Trabeculae and Pia Mater?

Answer 5

Arachnoid trabeculae subtly blend with the Pia Mater to create the illusion of continuous tissues.

Question 6

How do cerebral arteries and veins interact with Pia Mater?

Answer 6

Cerebral arteries and veins travel in subarachnoid space and are held against the Pia mater by connective tissue until the arteries penetrate the brain.

Question 7

Describe the location of the subarachnoid space and its uniqueness.

Answer 7

This is the only normal anatomically present space.
Lies deep to the Arachnoid Mater.
Lies superficial to the Pia Mater.

Question 8

What is the clinical significance of potential spaces in the brain?

Answer 8

Blood has no where to go. It will put pressure on the brain, and possibly lead to death. Must be drained

Question 9

Define an epidural hematoma. Cause?

Define a subdural hematoma.Cause?

Answer 9

Epidural–A bleed or hemorrhage in the space between the periosteal layer of the Dura Mater and the skull. Cause by a blow to the head.

Subdural–A bleed or hemorrhage in the space between the dura mater and the arachnoid mater. Caused by a high velocity change such as banging into the wall. The brain crashes into the skull and bleeding occurs.

Question 10

There are 3 dural layer folds called Reflections or Septums.

Describe
Falx Cerebri
Tentorium Cerebelli
Diphragma Sellae

Answer 10

Falx Cerebri intervenes between the two cerebral hemisphere (sickle shaped). Is continuous with the next…

Tentorium Cerebelli between the cerebellum and the cerebral hemispheres. (tent covering the cerebellum. attaches to wall of skull)

Diphragma Sella small reflection covering the pituitary fossa and admitting the infundibulum through a small perforation. (infundibulum is part of the thalamus)

Question 11

Dural Venous Sinuses
What are they?
What materials compose them and why?
Shape?

Answer 11

Dural layers are often separated at the major dural reflections to create a channel or “venous Sinus” in which cerebral veins drain.

Composed of dura mater lined with epithelium. The epithelia acts as a vein (all veins have epithelial lining)

Wedge shaped in cross section.

Question 12

What is the path of the sinuses?

Answer 12

Superior Sagittal Sinus (around the top of the brain)
Confluence of Sinuses (in the back)
Transverse Sinus (around the edges)
Sigmoid Sinus
Jugular bulb to Jugular vein

Question 13

What is a physically significant feature of the venous drainage system?

Answer 13

It is a valveless system. There are no valves to pump blood back to the brain. If there is a blockage, there are multiple routes (collaterals) for blood to detour. One way valves would prohibit this system from working.

Question 14

Describe the blood supply to dura mater.

Answer 14

Meningeal arteries travel through the periosteal layer of the Dura Mater only. They originate from the maxillary, ophthalmic, occipital, and vertebral arteries. (From carotid and vertebral arteries)(risk of infection)

Question 15

What parts of the brain are pain sensitive?
Which chief nerve?
Localization?

Answer 15

Dura Mater and proximal portions of blood vessels at the base of the brain are pain sensitive.

CN 5 Trigeminal N. goes to Dura mater
CN 10 goes to posterior Dura mater

A person can pinpoint where the pain is even though it is super deep if the pain is near a meningeal artery. Pain near a dural sinus, posterior, or floor of anterior cranial fossa will be referred to trigeminal nerve innervation or post. neck and ears.

Question 16

What do we need to know about Subarachnoid Cisterns?

Answer 16

The CSF is primarily produced in the four ventricles and passes into the cisterns through 3 individual foramen (small passages) of the 4th ventricle. The cistern provide separation between the arachnoid and pia maters.

Question 17

What is the Brain Blood Barrier? at least from a subarachnoid point of view?
What is the only way to get CSF into venous blood?

Answer 17

CSF in the subarachnoid space is separated from the venous blood by a layer of arachnoid, meningeal dura, and endothelial lining of sinus.

CSF must pass through Arachnoid Villus to get to a dural sinus.