1.4 Flashcards
Layers and spaces of the meninges
- Skull
- Epidural space
- Dura mater
- Subdural space
- Arachnoid mater
- Subarachnoid space
- Pia mater
- Brain
Special structures of the cranial dura
Dural folds create separations between parts of the brain:
- falx cerebri: separate R and L cerebral hemispheres
- tentorium cerebeli: occipital from cerebellum
- falx cerebelli: separates R and L cerebellum
- diaphragma sella: diaphragm over hypophyseal fossa formed by meningeal dura layer
Cranial arachnoid mater
Thin layer with trabeculae that attach it to the pia mater
Avascular
Cranial arachnoid mater and CSF
Subarachnoid space is filled with CSF.
It enlarges in some areas to form cisterns.
Arachnoid granulations
Arachnoid vili that protrude into the dural sinuses.
A group of villi = granulation
Transport much of the CSF into the venous circulation.
Cranial pia mater
Thin, usually only one cell deep
Vascular
Adheres to brain tissue
Acts as barrier
- degrades neurotransmitters
- separates subarachnoid matter from brain tissue
Intercranial hemorrhages
Spinal pia
Forms special structures
- filum terminale
Venous sinuses
Formed by dura mater
Collect blood from brain and scalp (via emissary vv.)
Drains into internal jugular vv.
Major dural sinuses
Superior sagittal
Inferior sagittal
Straight
Confluence of sinuses
Sigmoid sinus
Cavernous sinus
Joins several sinuses deep in the cranium
Can be site of infection and embolus
Cavernous sinus thrombosis
Often related to adjacent infection
Dural venous sinus
Separated layers of dura
Venous circulation
Ventricles of the brain
Ependymal cells line the cavities
Contains choroid plexus which produces CSF
R and L lateral ventricles
In the cerebral hemispheres
Largest of the ventricles
3rd and 4th ventricles
Along the midline
Interventricular foramen
AKA foramina of monro
Lateral ventricles to 3rd ventricle
Cerebral aqueduct
AKA aqueduct of sylvius
3rd ventricle to 4th ventricle
Median and lateral apertures
Median - foramen of magendie
lateral - foramina of luschka
From 4th ventricle to subarachnoid space
CSF
Clear, colorless
Circulates through ventricles and within subarachnoid space
Returns to venous circulation through arachnoid villi
CSF circulation
Ventricles –> subarachnoid space –> dural sinuses/ venous circulation
Blood brain barrier
Protects the brain
- vascular cells
- astrocytes
- microglia
- basal lamina
2 main arteries of the intracranial structures
Internal carotid aa
Vertebral aa
Join together to create the Circle of Willis
Vertebral artery course
Through transverse processes of cervical spine
Gives branches to spinal arteries
Join to form the basilar artery
Basilar artery
Primarily supplies posterior cerebral a.
Gives rise to
- pontine aa
- cerebellar aa
Circle of Willis
Gives rise to
- anterior cerebral a
- middle cerebral a
- posterior cerebral a
Cerebral arterial supply
3 branches of the Circle of Willis supply most of the cerebral hemispheres
Venous drainage of the CNS
We have superficial (external) and deep (internal) cerebral veins. Much of our venous drainage involves venous sinuses.
Venous drainage has multiple paths, but ultimately the majority of the cranial blood flow empties into the internal jugular vein.
CSF circulates within which space?
subarachnoid space, ventricles of the brain, and central canal of the spinal cord
Which layer of meninges forms the dural sinuses?
meningeal layer of the cranial dura mater
What do the venous sinuses do?
Collect blood from the brain and form emissary veins and also receive CSF from the subarachnoid spaces
Where do venous sinuses empty their contents?
the superior jugular bulb of the internal jugular vein
Where is CSF made?
choroid plexuses of the ventricles of the brain
What is the function of CSF?
- forms a protective fluid cushion for the brain and spinal cord and is a recipient of brain metabolites
- immunological defense of the brain
- maintenance of normal pH of the brain and spinal cords environment
- reducing pressure of the brain
Internal carotid artery
The internal carotid artery, one of the paired terminal branches of the common carotid artery, forms numerous branches supplying the brain and participated in the formation of the cerebral arterial circle of Willis.
80% of cerebral blood flow comes from ___ and 20% comes from___.
internal carotid; vertebral arteries
