Protection of the Brain Flashcards
(30 cards)
Describe how the brain is protected?
- by bone, meninges, and cerebrospinal fluid
- harmful substances are shielded from the brain by the blood-brain barrier
Describe the Meninges
Three connective tissue membranes lie external to the CNS:
Dura mater, arachnoid mater, and pia mater
What are the functions of the meninges?
- To **cover and protect **the CNS
- protect blood vessels and enclose venous sinuses
- contain cerebrospinal fluid (CSF)
- form partitions within the skull
Describe the Dura Mater
- dura = tough
- Leathery, strong menninx composed of two fused fibrous connective tissue layers
- The two layers separate in certain areas and form dural venous sinuses
- Three dural septa extend inward and limit excessive movement of the brain
Describe what the dural venous sinuses do
Sinuses collect the venous blood from the brain and direct itinto the internal jugular veins of the neck.
Sinus within the longitudinal fissure is the superior sagittal sinus
What are the three dural septa that extend inward and limite movement of the brain?
Falx cerebri
Falx cerebelli
Tentorium cerebelli
Where is the Falx cerebri located?
Falx cerebri is the fold that dips into the logitudinal fissure.
It’s anterior attachment point is the crista galli
Where is the falx cerebelli located?
The falx cerebelli runs along the vermis of the cerebellum
Where is the tentorium cerebelli located?
The tentorium cerebelli is horizontal dural fold extends into the transverse fissure
What is Arachnoid Mater?
Arachnoid = resembling a spider [web]
The middle meninx, which forms a loose brain covering
What separates Arachnoid Mater from Dura Mater?
Subdural space separates dura mater from the arachnoid mater
What lies beneath the arachnoid space?
A wide subarachnoid space that contains CSF and large blood vessels
What is the Arachnoid Villi?
The arachnoid villi protrude superiorly into the dural sinuses and permit CSF to be absorbed into venous blood
What is Pia Mater?
pia = tender
Deepest meninx composed of delicate connective tissue that clings tightly to the brain at each sulcus and gyrus
Describe Cerebrospinal Fluid (CSF)
- watery solution similar in composition to blood plasma
- -contains less protein and different ion concentrations than plasma
What are the functions of Cerebrospinal Fluid (CSF)?
- Forms a liquid cusion that gives buoyancy to the brain and spinal cord
- Prevents the brain from crushing under its own weight
- Protects the CNS from blows and other trauma
- Nourishes the brain and carries chemical signals throughout it
Where is Cerebrospinal Fluid (CSF) located?
Contained within the ventricles & central spinal cord plus surrounds the brain and spinal cord (in subarachnoid space)
- Paird Lateral Ventricles (right and left)
- Third Ventricle
- Fourth Ventricle (between the pons and the cerebellum)
- Cerebral Aqueduct (canal which connects the third and Fourth Ventricles)
What separates the paired Lateral Ventricles (left and right)?
The thin membrain called the septum pellucidum
Where is the Third Ventricle located?
between the two halves of the thalamus
How does the Third Ventricle communicate with the Lateral Ventricles?
via the interventricular foramen
Where is Cerebrospinal Fluid (CSF) prodced?
CSF is produced by the Choroid Plexuses
Describe the Choroid Plexuses
- clusters of capillaries which hang from the roof of each ventricle
- have ion pumps that allow them to alter ion concentrations of the CSF
- help cleanse CSF by removing wastes
Clinical Correlates of protection of the brain:
What is Hydrocephalus?
Hydrocephalus is swelling in the ventricles and the sub-arachnoid space.
Clinical correlates of Protection of the Brain
What causes hydrocephalus?
A mis-match in the rate of CSF production vs. removal
