BMC L4 Flashcards
What are the meninges?
3 layers of protective tissue:
Dura mater
Arachnoid mater
Pia mater
Surrounding the brain + spinal cord.
Meninges of brain + spinal cord connected via magnum foramen
Describe the position of the dura mater
Most superior of the meninges - outermost layer
Describe the structure and function of the dura mater
dura mater = hard mother
dura - durable
-2 layers:
-fibrous outer layer - fibrous because containds collagen - fibrous layer fuses with endosteum
-smooth meningeal inner layer
Fibrous outer layer makes it tough + inflexible, therefore, this allows it to protect the brain from displacement
Epidural Space
Potential space between dura mater of spinal cord and wall of vertebral column. Contains
-arteries
-lymphatics
-fatty tissue
Describe the position of the arachnoid mater
Middle layer of meninges
State the function of the arachnoid mater
Arachnoid mater has projections which project into the sinuses of the dura mater, called arachnoid granulations / arachnoid villi
These transfer CSF from ventricles into blood (CSF ABSORPTION)
Subarachnoid Space
Space between arachnoid mater and pia mater
Filled with CSF
All blood vessels + cranial nerves which enter the brain run through the subarachnoid space
arachnoid - blood vessels run through similar to shape of “spider web”
Describe the location and function of the Pia Mater
Inner most layer of meninges - soft
Adheres closely to the brain and runs through into sulci + fissues of cortex
It then projects into ventricles
Then fuses with ependyma
Ependyma is a membronous lining of the ventricles
Forms choroid plexi - (where ependyma and pia mater meet)
Which produce CSF
Diagram of meninges
- Skin of Scalp
- Perosteum
- Bone of skull
- Dura mater - both layers
- Subdural space
- Arachnoid mater
- Arachnoid villus
- Subarachnoid space
- Pia mater
Where is cerebrospinal fluid produced
Produced by choroid plexi in ependyma of ventricles of brain
Where is cerebrospinal fluid found?
In ependyma, membraneous lining in ventricles of brain
Subarachnoid space
Central canal, a space within the spinal cord
Functions of CSF
- Cushions brain + spinal cord
- Supplies nutrients to brain + spinal cord + removes waste
CLEAR LIQUID, IT IS A FILTRATE OF BLOOD, produced by filtering blood
Why is CSF similar to saliva?
Filtrate of blood (both produced by filtering blood)
CSF circulation
Lateral ventricle choroid plexus - CSF - Lateral ventricle
INTRAVENTRICULAR FORAMEN
3rd ventricle choroid plexus - CSF - 3rd ventricle
CEREBRAL AQUADUCT
4th Ventricle choroid plexus - CSF - 4th ventricle
LATERAL + MEDIAL APERTURES
Subarachnoid space
Arachnoid Villi
Heart Lungs
REFER TO DIAGRAM L4
What is glymphatics
Drainage system of the brain
Explain how glymphatics works as a drainage system of the brain
- AQP4 channels between astrocyte end feet + blood vessels carry CSF into parenchyma
- In parenchyma, CSF mixes with intersititual fluid (ISF)
- This mixture, is known as the drainage system of the brain
- This mixture of CSF and ISF enters the perivascular space which surrounds the veins
- It removes waste (drains the waste), e.g. beta amyloid peptide
What affect does sleep have on glymphatics
More CSF enters the glymphatic system during sleep
Give 2 special features of ependymal cells
- Rich blood supply
- Modified ependymal cells pump Na+, H2O, folllowed by osmosis
Subdural space
Potential space between dura mater and arachnoid mater
The cranial cavity
The cranial cavity is the skull / crainium
It is a rigid box
It consists of blood vessels, CSF, brain
How does the cranial cavity communicate with the vertebral column?
Via the foramen magnum
Intracranial pressure
- If extensive bleedig, excessive tumout growth in cranial cavity, this leads to increased intracranial pressure
-This is because cranial caivity is a rigid box
-Not enough space for growth
What is the blood brain barrier?
BBB
Highly selective permeable barrier between circulating blood + extracellular CNS fluid
Formed by blood capillary endothelial cells - joined together by tight junctions
Function of BBB
Restrict filtration of materials into CSF by choroid plexi
including
-bacteria
-toxins
-drugs
What is the BBB made of?
- Blood capillary endothelial cells
- Basement membrane
- Feet of astrocytes (wrap around capillaries)
What are the 4 levels of protection of brain?
- Skull / Cranial Cavity / Cranium
- Meninges
- Blood Brain Barrier
- Cerebrospinal Fluid
Circumventricular organs
- Not protected by BBB
-interact directly with peripheral blood
if we monitor blood chemistry, we see hormone released from circumventricular organs to blood stream
Two examples of circumventricular organs
-pituitary gland
-pineal gland
