Meninges, ventricles, and cerebrospinal fluid Flashcards
cranial meninges
these are the three connective tissues that are surrounding the brain
- the dura mater
- arachnoid mater
- pia mater
- these are anchored to the skull and the brain is suspended within the meninges
- these extend around the spinal cord and are continuous throughout the CNS
functions of the cranial meninges
- cover and protect the brain
(protects against foreign substances, trauma, etc and separates the soft tissue of the brain from the bones of the cranium) - enclose and protect blood vessels
( support vessels supplying the brain and form some of the venous sinuses draining blood from the brain) - stabalize the brain within the skull
- contain the CSF
dura mater
- this is the outer layer of the meninges
- this is the thickest layer
- contains two layers: the periosteal layer and the meningeal layer
blood vessels are between the two layers
periosteal layer
- fused to the periosteum on the inner aspect of the skull
- this is one of the fibrous layers of the dura mater
meningeal layer
- this is next to the arachnoid mater
- this is one of the fibrous layers of the dura mater
dural venous sinuses
- these are large collecting veins that drain the blood from the brain
- these are formed within the space of the periosteal and meningeal dura
what are the key sinuses
- superior sagittal sinus
- inferior sagittal sinus
- transverse sinuses
- straight sinus
- confluence of sinuses
which sinuses are in teh falc cerebri
- superior sagittal sinus
- inferior sagittal sinus
straight sinus
this connects the inferior sagittal and superior sagittal sinuses
receives blood from the superior cerebellar veins and inferior sagittal sinus and drains into the confluence of sinuses.
confluence of sinuses
- this is posterior and this is where the superior, straight, and transverse sinuses merge
what are cranial dural reflections
- these are the septa
- these are where the meningeal layer of dura extends deep into the cranial cavity between sections of the brain
- functions:
- subdivide cranial cavity
- support the brain
- limit movement of the brain
falx cerebri
- this is within the longitudinal fissure between the cerebral hemispheres
- this contains the inferior sagittal sinus and the superior sagittal sinus
- this is what can stop one hemisphere of the brain from moving in a traumatic force, putting excess strain on the corpus callosum
falx cerebelli
- this is between the two cerebellar hemispheres
tentorium cerebrelli
- this is between the occipital lobes of the cerebrum and the cerebellum
- this supports and protects the occipital lobes
- the transverse sinus lies within it
arachnoid mater
- this is the middle layer of the meninges
- this is deep to the dura mater
- this is a thin, avascular, semitransparent membrane visibly covering the brain
- contains arachnoid granulations
arachnoid granulations
- send CSF from the subarachnoid space into the blood within the superior sagittal sinus
- these are finger like extensions
pia mater
- this is the inner most layer of the meninges
- thin delicate CT tightly attached to the brain
- follows all the contours of the gyri and sulci
- supports large cerebral blood vessels
subarachnoid space
- this is between the arachnoid and pia mater
- this contain the arachnoid trabeculae
- this contains the CSF
- this also contains blood vessels
arachnoid trabeculae
web like threads extending across the subarachnoid space from arachnoid mater to pia mater
cerebrospinal fluid
this is a colorless fluid that circulates in the ventricles and subarachnoid space
-this is produced in the choroid plexus found within the ventricles of the brain
choroid plexus
- specialised ependymal cells and highly permeable capillaries
- choroid plexus also removes waste from the CSF and alters its composition as needed
- CSF is constantly being produced
how does CSF move through and around the brain
- movement of cilia on the ependymal cells
- movements of the vertebral column moving it around the spinal cord
- pressure from the constant production forcing it out through the arachnoid granulations
functions of CSF
- buoyancy: brain floats within the CSF
- protection: brain floats in the CSF and does not sit against the skill
- environmental stability: maintains the environment surrounding the brain
- transports hormones, nutrients, chemicals, wastes brain
brain ventricles
- fluid filled chamber
- there is one within each hemisphere, one in the diencephalon, and one between the pons and cerebellum
two lateral ventricles
- one is in each hemisphere
- they are separated by the midline septum pellucidum
- there is no direct connection between the two but they each communicate with the 3rd ventricle
- has a complex shape
- has an anterior horn, body, posterior horn, and inferior horn that extends into the temporal lobes
3rd ventricle
- this is midline
- this is between the right thalamus and left thalamus
- there is a “ hole” in this one that is formed from the connecting left and right thalami
interthalamic adhesion
this connects the left and right thalami and creates a “hole” in the 3rd ventricle
4th ventricle
- this is between the pons and the cerebellum extending into the superior portion of the medulla oblongata
interventricular foramen
there are two of these
each of these connect the lateral ventricles to the 3rd ventricle
cerebral acqueduct
- this connects the 3rd ventricle to teh 4th ventricle
- a thin canal in the mescepalon
how can CSF leave the 4th ventricle
- lateral aperture (this is on either side of the 4th ventricle)
- medial aperture (this is at the midline, posterior aspect of the 4th ventricle)
- central canal of the spinal cord
describe the circulation of CSF
- lateral ventricle –> interventricular foramen of monro -> 3rd ventricle
- 3rd ventricle–> cerebral aqueduct -> 4th ventricle
- 4th ventricle-> one of these routes into the subarachnoid space:
- paired lateral apertures, midline median aperture, central canal of spinal cord - CSF enters the subarachnoid space
- CSF flows into arachnoid granulations, which transport it into the dural venous sinuses
blood brain barrier (BBB)
this is the separation of the CNS from the general circulation
function of the BBB
tightly regulates what can leave the blood vessels and enter the space surrounding the brain tissue
formation of the BBB
- it is formed by the interconnected capillaries that are connected via tight junctions
- astrocytes surround the capillaries
what is the importance of the tight junctions between teh capillaries of the BBB
- these prevent materials from diffusing between the epithelial cells
astrocyte perivascular feet
these are projections off of the astrocyte that surround teh cappilaries
importance of the astrocytes for the BBB
these restrict the permeability of hte capillary endothelial cells
- they are able to secrete chemicals for resrticting
describe transport across the BBB
- it is selective and directional
- it will pump things like glucose against its gradient because the neurons need a constant supply of glucose so no matter what the concentration is in the blood it will transport it into the brain
what are the parts of the BBB variations
- hypothalamus: allows for hormone diffusion
- pituitary gland: allows for hormone diffusion
- pineal gland: helps with the sleep wake cycle
- choroid plexus: production of CSF
these all have to have specialized capillaries that have increased permeability
