Protection of the nervous tissue Flashcards
(27 cards)
how is the cns protected
the skull encases the brain and the vertebrae shield the spinal cord
-connective tissue also sheathes the brain and spinal cord
how is the pns protected
PNS axons are bundled into nerves covered by three layers of protective connective tissues. the endoneurium, perineurium, and epineurium
endoneurium
a thin fibrous membrane that sheathes each axon in a nerve
perineurium
a fibrous sheath that surrounds bundles of axons that are gathered into fascicles
epineurium
a fibrous sheath that surrounds the nerve. the nerve is made up of multiple fascicles
meninges
the collective term for the three membranes that surround the brain and spinal cord and act as a protective barrier , help anchor the brain, and prevent it from moving in the skull.
Cerebrospinal fluid (CSF)
fills the space between two of the meninges, cushions the brain and spinal cord, and flows through the brain and spinal cord
three meningeal membranes
dura mater, arachnoid mater, and pia mater
dura mater
the outer most meningeal layer that is a strong, thick, fibrous membrane that extends from the brain to the most caudal region of the vertebral column
venus/dural sinuses
blood vessels within the outer and inner layers of the dura mater
outer layer of the dura mater
tightly applied to the interior wall of the skull
the inner layer of the dura mater
has several folds that divide the cranial cavity , creating subdivisions of the brain that act to restrict movement of the brain
epidural space
a thin space containing fat separates the vertebral dura and vertebral bone. vertebral dura is not attached to the bone
subdural space
space beneath the dura mater that is filled with connective tissues, fat, and blood capillaries
arachnoid mater
the middle meningeal layer
subarachnoid mater
the space beneath the arachnoid mater that is filled with CSF and also contains the largest blood vessels that supply the brain. spider like extensions that extend from the arachnoid mater to the pia mater and hold them together
arachnoid villi
small pockets of the arachnoid mater that protrude into the dural/venous sinuses. they allow CSF to exit the space beneath the arachnoid mater and enter the bloodstream
pia mater
a thin membrane that is tightly fitted over every prominence and depression in the irregular surface of the brain and spinal cord
Functions of the CSF
-protection: supports the weight of the brain and forms a cushion around it
-transport: supplies nutrients to the brain and bloodstream and removes waste
choroid plexus
a network of blood vessels and ependymal cells that forms the CSF. it filters wastes and foreign substances out of the CSF
CSF circulation
-from the choroid plexus through the ventricles of the brain
-the rest moves into the subarachnoid space, where it is absorbed into the bloodstream though arachnoid granulations that are one way valves.
-meaning CSF can move out of the subarachnoid space but blood cannot move in
ventricles of the brain
consists of two lateral ventricles (right and left) the third ventricle, and the fourth ventricle. all interconnected by canals
hydrocephalus
when the skull enlarges and fills with CSF
Blood Brain Barrier
prevents harmful substances from entering the brain from the blood. protects from blood-borne infections and from the normal fluctuation of solutes in the extracellular environment. Not very protective against lipid-soluble substances
