Meningeal Coverings Flashcards
What are the meningeal coverings and their functions?
- Dura Mater= fat, thick covering, adhering to skull
- Arachnoid= forms barrier, has trabeculae connecting to pia.
- Pia = translucent film that is on the brain
What are the major differences between spinal and cranial meninges?
- Pia mater in the brain could be very thin, versus could thicken in the spinal cord to form denticulate ligaments (thickened arachnoid trabeculae) and filum terminale
- the spine does normally have an epidural space, between spine and vertebral periosteum.
- spinal cord also has a large lumbar cisterna = large subarachnoid cisterna, since the spinal cord is shorter than the vertebral canal
What is the blood-CSF barrier?
- CHOROIDAL EPITHELIUM, are the ependymal cells of the CNS, but more restricted at the level of the choroid plexus (tight junctions).
- Decides what in the blood will exit to enter the CSF
What is the Choroid Plexus?
- Specialized structure, made up of: fenestrated capillaries to let things out, pia, choroid epithelium
- Makes 60% of the CSF
What is the origin of CSF?
60% Choroid Plexus
30% Capillary Bed
10% Metabolic
Made in the ventricles, travels out of the various apertures, into cisterns through the tentorial notch and into the venous sinuses through the arachnoid vili.
What is the function of CSF?
- brain support- buoyancy
- spatial buffering sys
- sink for substances made that need to be removed/reabsorbed
- route for spread of “neuroactive” hormones
What is the composition of CSF?
about the same as blood in: sodium, chloride, bicarbonate and osmolarity
less than blood: potassium, calcium, glucose AA, pH, cholesterol and protein
More than blood: magnesium and creatinine
- composition controlled by blood-CSF barrier
- Total of about 150 ml of CSF, 250 uL/min
What blood vessels are responsible for an epidural, subdural, subarachnoid cerebral hemorrhage?
Epidural: trauma between bone and dura; bleeding of periosteal arteries or veins.
= middle meningeal artery
Subdural: damage to veins where they enter venous sinuses
subarachnoid: damage to CNS artery/vein such as rupture of cerebral artery, burst aneurysm
What are the important features of the dura mater?
- provides mechanical strength
- contains venous sinuses
- own blood supply
- pain sensitive, innervated by trigeminal and cerivcal nerves
How does the CSF enter the venous sinus?
Through arachnoid vili
What should you look for when testing CSF?
Glucose and protein levels.
- bacterial tend to drive down glucose levels
- viral, you’ll see an increase in inflammation in the meninges
- protein levels tend to increase, esp albumin
What is arachnoid trabeculae?
strands of collagenous connective tissue and scattered cells that suspend the the brain.
connect the arachnoid to the pia mater.
What is hydrocephalus?
Excessive accumulation of CSF within the ventricles or subarachnoid spaces.
If a person is young, the person’s head starts to expand as well because their bones aren’t fused
What are circumventricular organs?
Organs in the brain that lack a blood brain barrier around the 3rd and 4th ventricles, and have high neural tissue.
Impt fxn for: body fluid regulation, cardiovascular functions, immune responses, thirst, feeding behavior and reproductive behavior.
Examples:
Sensory: area postrema
Secretory: p. pituitary
Tanycytes are specialized ependymal cells that overlie CVO.
What is a brain herniation?
added pressure to the brain as it is pushed into smaller spaces.
Could be caused by hematoma, tumor..
