Ch. 2 - Meninges & Ventricles Flashcards
What are the 3 connective tissue layers over the CNS that function in protection?
- Dura mater
- Arachnoid mater
- Pia mater
What meningeal layer is known as the “tough mother” and is the extremely sturdy, outermost protective layer, thick and inelastic?
Dura
What is stuck to the periosteum of the skull?
Outer dura mater
What is a very thick covering over the brain and spinal cord?
Inner dura mater
What is between the outer and inner dura mater layers?
Venous sinuses
The inner dura mater has a midline belayer extension btw the cerebral hemispheres called what?
Falx cerebri
The inner dura mater extends btw the occipital lobes and the cerebellum known as the what?
Tentorium cerebelli
What is the potential space btw the dura and the arachnoid /c cerebral veins?
Subdural spaces
What is epidural bleeding usually caused by?
Traumatic shearing of the meningeal arteries
What meningeal layer is “a thin ‘spider-web-like’ avascular layer?”
Arachnoid
What is the space btw the arachnoid and pia?
The subarachnoid space
What contains the large surface arteries supplying the brain?
Subarachnoid space
A subarachnoid hemorrhage is a form of a stroke from a ruptured what?
- Cerebral a.
2. Congenital “berry” aneurysm
What is a positive test for a subarachnoid hemorrhage?
Blood in the CSF
The subarachnoid space enlarges in several places to form the what?
Cisterns
What is the cistern located dorsal to the medulla and inferior to the cerebellum?
Cistern magna (cerebellomedullaris)
What cistern is anterior to the pontomedullary junction?
Pontine cistern
What cistern is anterior to the midbrain?
Interpeduncular cistern
What cistern is posterior to the midbrain, and superior to the cerebellum
Superior cistern
What cistern is caudal to the spinal cord (from L2 to S2)?
Spinal cistern
What meningeal layer is known as the “loving mother” very delicate, and adhered to the surface of the brain and spinal cord?
Pia
What meningeal layer intimately follows the surface into the depths of each sulcus?
Pia
Does the pia mater contain blood vessels?
Yes, small branches
Ventricles are a series of cavities within the brain that develop from what?
The lumen of the neural tube
The ventricles are lined /c what?
Ependymal cells (cuboidal glial cells)
The ventricles are filled /c what?
CSF
What ventricle is paired and consists of the anterior horn, body, posterior horn, and inferior horn?
Lateral ventricles
What part of the lateral ventricle is…
- anterior to the interventricular foramen, in frontal lobe
- boundaries are: septum pellucidum (medically), head of caudate nucleus (laterally), body of corpus callosum (superiorly), & genu of corpus callosum (anteriorly)
Anterior horn
What part of the lateral ventricle….
- central part, in parietal lobe
- thalamus forms the floor
- corpus callosum forms the roof
- lateral wall = body of caudate nucleus
- medial wall = septum pellucidum
- contains choroid plexus
Body
What part of the lateral ventricle…
- small posterior extension into the occipital lobe
Posterior horn
What part of the lateral ventricle…
- extends down into the temporal lobe
- floor & medial wall = hippocampus
- lateral roof = tail of caudate nucleus
- contains choroid plexus
Inferior horn
- Paired
- connection of each lateral ventricle into the anterior part of the 3rd ventricle
Interventricular Forman (of monro)
What ventricle is…
- midline
- occupies most of the diencephalon
- anterior boundary = terminal lamina
- extends back to cerebral aqueduct
- lateral walls = thalamus and hypothalamus
- floor = hypothalamus
- contains choroid plexus
3rd ventricle
Narrow canal btw the 3rd and 4th ventricles in the region of the midbrain and upper pons
Cerebral Aqueduct (of Sylvius)
Wide ventricle in region of Rhombencephalon
- floor = rhomboid fossa /c pons and rostra medulla anteriorly & cerebellum posteriorly
- extends from cerebral aqueduct rostrally to the central canal caudally
- contains choroid plexus
4th ventricle
Paired lateral openings at the end of the R and L lateral recesses for passage of CSF out of the 4th ventricle into the cistern a magna
Lateral aperture (aka foramen of Luschka)
The midline terminus of the 4th ventricle allows CSF to leave the fourth ventricle into the cistern a magna
Medial aperture (aka Foramen of Magendie)
Vascular network of Pial vessels /c the ependymal lining membranes which secrete the CSF
- located in the lateral, 3rd, and 4th ventricles
Choroid plexus
Where is the choroid plexus in the lateral ventricle?
- floor
- near the tip of the inferior horn, around the C-shaped course thru the ventricle body to the interventricular foramen (not in anterior and posterior horns)
- paired
Where is the choroid plexus in the 3rd ventricle?
- unpaired
- hanging from thin roof of 3rd ventricle
- continuous anteriorly via interventricular foramen /c choroid plexus of lateral ventricles
Where is the choroid plexus in the 4th ventricle?
- unpaired
- in roof of medulla, extending into lateral aperture
What 2 fluids are in the CNS?
- Interstitial fluid
2. CSF
What is interstitial fluid produces by? What does it surround?
Brain capillaries; each cell
What is CSF produced by? What does it fill?
Choroid plexus; ventricles & subarachnoid space
What do the capillary endothelial cells form?
Blood-brain barrier
What do the ependymal cells form?
Blood-cerebrospinal fluid barrier
The blood barriers are impermeable d/t what?
Tight junctions formed by astrocyte foot processes which surround capillaries
What are the 2 transport systems used with blood barriers?
- Passive facilitated diffusion
2. Mitochondria-driven active transport
What substance passes readily thru the brain barriers?
Lipid soluble substances
- clear watery fluid, /c a small amount of protein, electrolytes, glucose, and rarely lymphocytes
- produced by choroid plexus via capillary filtration & active secretion transport
CSF
What are the 3 functions of CSF?
- Cushions the brain
- Provides a homeostatic environment
- Provides a drainage system for waste substances (since there are no lymphatics)
Flow of CSF
_______ ventricles —> ________ foramen —> _____ ventricle —-> ________ aqueduct —> _______ ventricle —> formaina of _________ & _______ —> _________ space (aka cisterna magna)
Lateral ventricles —> interventricular foramen —> 3rd ventricle —-> cerebral aqueduct —> 4th ventricle —> formaina of Luschka & Magendie —> subarachnoid space (aka cisterna magna)
What allows the CSF to pass by bulk flow from the subarachnoid space into the superior sagittal sinus?
Arachnoid granulation
CSF pressure depends on what 2 things?
- Position
- Amount
Of fluid in the closed space of the skull
An obstruction of the CSF path results in backlog of CSF and a resultant increase in intracranial pressure, which diagnostic swelling of the _________. In a child, an increased __________ will be seen.
Optic disc (papilledema); head circumference
Inject radiopaque dye into tan artery, then cerebral x-ray shows the vessels
Angiography
X-ray information is processed by a computer and produces computerized images of sections thru various levels of the brain and brain stem
Computerized tomography (CT)
Magnetic field causes emission of radio waves which are interpreted by a computer to produce sections /c fine detail
Magnetic resonance imaging (MRI)
Injecting air into at ventricle, subarachnoid space of lumbar cistern
Pneumonencephalography
Contrast media is injected into subarachnoid space while on tilt table, then x-rays
Myelogram
Insert needle at L3/L4 or L4/L5 (distal to cord) to drain CSF for analysis
Lumbar puncture (spinal tap)
