week 1- protection of the brain Flashcards
the brain is protected by…
- cranium (skull)
- meninges
- blood brain barrier
- cerebrospinal fluid
what does the cranium do?
encloses brain to protect it from mechanical force
what are the meninges?
3 connective tissue membranes that cover external surface of brain and spinal cord
what is each membrane of the meninges called?
mater
what is the outermost membrane of the meninges called?
dura mater
what is the middle membrane of the meninges called?
arachnoid mater
what is the innermost membrane of the meninges called?
pia mater
what is outer dura mater?
strong, protective membrane that is double layered
what is the outer layer of the dura mater called?
periosteal layer
what does the outer periosteral layer attach to?
attaches directly to the inner surface of skull
what does the inner meningeal layer cover?
external surface of the brain
the two dural membranes are fused together but in areas where they seperate they enclose…
dural sinuses
what are dural sinuses?
channels that drain venous blood from the brain
what is dural folds(septa)?
tough, inward folds the help hold brain in position and prevent excessive movement
what is the arachanoid mater seperated from the dura mater with?
subdural space
what is the cavity found beneath the arachnoid membrane?
subarachnoid space
what does the subarachnoid space contain?
cerebrospinal fluid
what does cerebrospinal fluid do?
cushions brain further protecting from mechanical forces
what is pia mater?
very thin membrane that clings to surface of the brain
what does pia mater contain?
small blood vessels that supply oxygen and nutrients to brain and spinal cord
what does cerebrospinal fluid do?
- floats brain, reducing weight
- nourishes
- shock absorbing medium
how does CSF nourish the brain?
nourishes neural tissue and removes waste, functions as a diffusion medium between blood and neural tissue
where is CSF produced?
within the four ventricles of the brain by choroid plexus
what are the four ventricles of the brain interconnected with?
each other and central canal of spinal cord
where are the lateral ventricles found in the brain?
within each cerebral hemisphere
where is the third ventricle found in the brain?
diencephalon
where is the fourth ventricle found in the brain?
between cerebellum and brain stem
what is the choroid plexus?
a cluster of capillaries surrounded by ependymal cells, that are joined together by tight junctions. Produce CSF
once CSF is produced how does it flow?
- through venticles
- circulates through subarachanoid space, spinal meninges and through central canal
- is absorbed into dural sinuses via arachnoid villi
what does the blood-brain barrier do?
protects neural tissue from harmful substances and pathogens circulating in blood
what does the blood brain barrier mainly consist of?
endothelial cells and ‘feet’ processes of astrocytes
what is the blood-brain barrier permeable to?
- lipid soluble: oxygen, carbon dioxide, lipids, alcohol, nicotine and anaesthetics
- nutrients such as glucose
what is the blood-brain barrier impermeable to?
metabolic wastes, proteins, toxins, potassium ions, most drugs and antibiotics
how many arteries ascend the neck to deliver blood into cranium?
four
what four arteries ascend the neck to deliver blood into the cranium?
- right/left internal carotid arteries (either side of neck)
- right/left vertebral arteries (back of neck either side of vertebral column)
once blood is inside the cranium how many cerebral arteries supply blood to the cerebellum?
six
