Meninges Flashcards
What meningeal coverings are a part of the leptomeninges?
Arachnoid and pia mater
Generally, what is dura mater?
What’s its main fcn?
A thick connective tissue membrane that serves as the periosteum of the inside of the skull
- Main fcn is to suspend the brain (protect from trauma)
Explain the main layers of the dura mater.
Which contains the meningeal aa.?
What’s in b/w?
- Outer periosteal layer: firmly attached to skull; contains the meningeal aa.
- Inner meningeal layer: in close contact w/arachnoid and continuous w/spinal dura
- Dural venous sinuses
What is the space called b/w the dura and the cranium?
Trick- there is none (except in pathological conditions, then call it cranial epidural space)
What important things are contained in the spinal extradural space?
- Venous plexuses
- CT
What innervates the dura?
Anterior: CN V
Posterior: cervical nn. of cervical plexus
(this is a source of headaches)
Name and approximate the 4 main dural folds.
- Falx cerebri–vertically divides cerebrum
- Falx cerebelli–vertically divides cerebellum
- Tentorium cerebelli–horizontal tent over the cerebellum
- Diaphragma sellae–allows passage of pituitary stalk (pit sits beneath it)
What is the tentorial notch?
Exit pathway for the brainstem through the anterior tentorium cerebelli
What sinus is on the superior border of the falx cerebri?
Inferior border?
What connects them at their posterior ends?
- Superior sagittal sinus
- Inferior sagittal sinus
- Straight sinus
What sinus is at the falx cerebelli, against the occiput?
- Occipital sinus
- What are the dilated spaces at the external occipital protuberance?
- What are their horizontal extensions?
- What is the continuation of #2, into the IJV?
ConTraSig
- Confluence of sinuses
- R and L transverse sinuses
- R and L sigmoid sinuses
Where are the paired cavernous sinuses located?
What connects them?
- Lateral aspect of the body of the sphenoid
- Intercavernous sinus
What sinus runs along the inferior surface of the lesser wings of the sphenoid?
- Paired sphenoparietal sinuses
What sinuses run thru the petrous part of the temporal bone?
Which one ends at the IJV?
- Paired superior petrosal sinuses and paired inferior petrosal sinuses
- Inferiors ones end at IJV
(they come from cavernous sinus)
What sinus sits just posterior to the sella turcica of the sphenoid?
Basilar sinus
What do emissary vv. do?
What’s a pathology associated w/them?
- They connect the extracranial veins to the dural venous sinuses inside the cranium.
- Pathway for infection to spread from face/scalp to brain
Fcn of arachnoid trabeculae?
Suspends the brain
Where is CSF drained into?
Through what structures?
From where?
- Dural venous sinuses (to venous system)
- Arachnoid villi (clusters of villi = granulations)
- From: subarachnoid space
Besides arachnoid villi, what prevents CSF from leaking from the subarachnoid space into the veinous system or from the dura back into the CSF?
Arachnoid barrier containing tight junctions
Why does CSF flow naturally from the SAS into the dural venous sinuses?
If this was altered, what would happen?
- Pressure in SAS higher than that of venous sinuses
- If this was reversed, venous blood could not get back into SAS because of valves in arachnoid villi
What is on the side of pia mater opposite the arachnoid mater?
Astrocyte end feet that carpet the surface of the CNS
What layers are on either side of the spinal epidural space?
- Periosteum
- Dura
Spinal dura and arachnoid mater end at what vertebral level?
S2
The spinal cord ends at what vertebral level?
Where would be a safe place to perform an LP?
- L1/L2
- L3/L4
What meningeal layer provides the filum terminale?
Pia mater
What meningeal layer are denticulate ligaments made of?
Pia mater
What type of bleed would probably be caused by tearing a cerebral vein?
Subdural bleed
What type of bleed would probably be caused by tearing a cerebral artery?
Subarachnoid bleed
What type of bleed would probably be caused by tearing a meningeal artery?
Epidural bleed
What brain vesicle contains the lateral ventricles?
Third ventricle?
Fourth ventricle?
- Telencephalon
- Diencephalon
- Rhombencephalon
Explain the pathway of CSF flow in the ventricles to the SAS
2 lateral ventricles -> 2 interventricular foramina of Monro -> 3rd ventricle -> Cerebral aqueduct of Sylvius -> 4th ventricle -> Median aperture (foramen of Magendie) and 2 lateral apertures (foramina of Luschka) -> SAS
Name the different parts of a lateral ventricle.
- Frontal (ant) horn
- Temporal (inf) horn
- Occipital (post) horn
- Body (sup)
- Atrium (b/w them)
What secretes CSF?
Where is this usually found?
- Choroid plexus
- Roof of 3rd + 4th ventricles, + medial wall of lateral ventricles
What is the nl rate of CSF produced/day?
How much do we have ahorita?
How much of this is in the ventricles?
- 500mL/day
- 90-150 mL
- 23 mL in ventricles (rest in SAS)
What types of cells surround the choroid plexus?
What is a second, special name for these cells?
Specialized ependymal cells, interconnected by tight junctions.
- These cells are specialized as a secretory epithelium called the choroid epithelium.
What is the intervening neural tissue b/w the inner lining of the ventricle and the pia mater?
There is none
Besides pia mater and specialized ependymal cells, what else is invaginated inside the choroid plexi (the 3rd layer)?
Vascular CT (bv’s)
What area of SAS is situated b/w the medulla and the inferior surface of the cerebellum?
Cisterna magna
What are a few main functions of the CSF?
- Mechanical support/cushioning
- Removal of metabolites
- Route to spread neuroactive hormones
What are 3 key facts about the composition of the CSF, regarding proteins, glucose, and salts, as compared to normal serum?
- Trace protein in CSF
- Less [glc], [Ca2+], [K+] vs. serum
- More [Na+], [Cl-], [Mg2+] vs. serum
What is hydrocephalus?
Explain the 2 main types of hydrocephalus.
Dilation of the ventricles
- Communicating: obstruction occurs after CSF leaves the ventricles, hence the ventricles can still communicate
- Non-communicating: obstruction occurs b/w the ventricles, most often the cerebral aqueduct (“aqueductal stenosis”)
What are the 2 circumventricular organs that we need to know?
What are defining characteristics and some key facts about circumventricular organs?
- Area postrema (sensory) and neurohypophysis (secretory)
- Lack BBB; extensive vasculature;
- Play key role in Na/H2O balance, CV regulation, energy metabolism, and immunomodulation
What is the area prostrema thought to be responsible for?
Vomiting (chemo can affect this area)
To which part of the lateral ventricles is the interventricular foramen attached?
Anterior/frontal horn
What a. runs thru the cavernous sinus?
ICA
