Lecture 10; 9/18 Flashcards
Test 2
What is in the subarachnoid space?
That is the potential space
2 subarachnoid blood vessles
Nothing else
Describe the epidural space
Above the dura layer
Filled with fat tissue and blood vessles
In what area do you give a spinal block?
Subarachnoid space
What risks do you run with doing a spinal block?
Puncture of the spinal cord because closer in the subarachnoid space
Why does a spinal block work faster than an epidural?
Epidural is given in the epidural space which has lots of fat so medication spreads slower
Where do you give an epidural?
In the epidural space
What risks do you run with giving medications in the epidural space?
Lipidphillic drugs get sucked into fat tissue and have longer onset and take longer to wear off
What are the venous blood vessels called in the epidural space?
Posterior/anterior internal vertebral venous plexus
If we run the risk of puncturing the spinal cord during a spinal then….
Its best we do a spinal in a place after the physical cord ends
Where does the spinal cord start?
Medula Oblongata
Where are your spinal cord enlargements?
C3-C6
T11-L1
Where does the spinal cord end?
Conus Medullaris
L1
Where is the cervical enlargement? Why do we have this?
C3-C6
Extra neurons d/t the brachial plexus (shoulder)
Where is your lumbar enlargement? Why do we have this?
T11-L1
Extra neurons d/t lumbar plexus and siatic nerve
What is under the conus medullaris?
After L1 is spinal roots that form spinal nerves
T/F: The dura layer goes all the way down to the bottom of the sacrum
T
Even though the cord ended, the spinal roots will have dura on them
What are the spinal roots called that flow after the conus medullaris?
Cauda Equina
“Horse Tail”
What is the Internum Filum Terminale?
Extension of pia mater
connective tissue inside the dursal sac that anchors the end of the cord to the end of the dural sac
What is the externum Filum terminale?
External anchor that connects the end of the dural sac to the coccyx
What is the purpose of the internum and externum filum terminales?
To keep the spinal cord from retracting up
What is another name for the dural sac?
Lumbar Cistern
What is in the dural sac?
Cauda Equina and CSF
Where does the dural sac end?
S2
Why is L4 area a great place for a spinal block?
Less risk of spinal cord puncture because the cord itsself ends at L1
We can easily find it via the illiac crest
Easier access midline
Where is the conus medullaris in a newborn?
L3
Where can CSF get stale in the spine at?
L-spine
What are the access points to give meds in the S spine?
S2 posterior sacral foramina
Sacral hiatus (Not used often)
Why do we want to give drugs at a 15 degree angle shift vs directly midline?
Incomplete fusion of the ligamentum flava
If it didnt completely fuse you’ll be missing the middle of it.
Going off center counteracts that
If you go midline with an incomplete fusion, you’ll go right through because you never felt that change in resistance, possibly piercing the spine
Where is the grey matter loacted on the brain?
More superior
Why are the blood vessles in the brain more superior?
Because the grey matter is more superior and its metabolism is higher because its where the decisions are being made
What is an epidural hematoma?
A bleed above the dura layer
Arterial bleed from cranial bone Fx
Moreso stays in one place but still bad
What is the Arachnoid trabeculae?
Pillars between the arachnoid layer and pia mater that has blood vessles and CSF
What is a subdural hemorrhage?
Bleed under the dura layer
Venous bleed from the sinouses in the brain
What is a subarachnoid hemorrhage?
Bleed under the arachnoid layer
Arterial… usually worse than a epidural bleed
Diffuses into tissues
What are the containers for CSF called?
Ventricles
What is normal ICP
10mmHg
Where is CSF produced?
In the choroid plexus in the ventricles
How many CSF ventricles are there?
4
Where is CSF reabsorbed back into the CVS? And why does this happen?
Arachnoid granulations
To keep the CSF within normal range
What are arachnoid granulations?
Pressure blow off valves that help equalize the pressure of CSF circulating
Where is the arachnoid granulations located?
Above the longitudinal fissure
What happens if the arachnoid granulations are blocked?
Communicative hydrocephalus
Increased ICP
What does the cerebellum do?
responsible for coordination
Where does the 4th ventricle empty CSF?
Median aperture
Lateral apertures
Central canal
What is the cerebellomedullary cistern?
Pool of CSF from the median aperture that circulates CSF around the cerebellum
What is communicating hydocephalus vs noncommunicating?
Communicating: CSF not being reabsorbed (arachnoid granulations); high pressures everywhere
Non communicating: Pathway blockage; enlarged ventricle
What is another name for the median aperature of the 4th ventricle?
Foramen of magendie
what is the exit point for CSF?
Central Canal
What is another name for the Cerebral aqueduct?
Aqueduct of sylvius
What does the cerebral aqueduct do
circulates CSF from 3rd to 4th ventricle
What is the other name for the interventricular foramen?
Foramen of Monroe
What does the foramen of monroe do?
CSF from lateral ventricles to 3rd ventricle
What are the lateral apertures?
exit point for CSF
Circulates CSF around the subarachnoid space
What is another name for Cerebellomedullary cistern?
Cisterna magna
Explain CSF flow
CSF is created in the choroid plexus of the ventricles
Lateral ventricles
Interventricular foramen (foramen of monroe)
3rd ventricle
cerebral aqueduct (aqueduct sylvius)
4th ventricle
median aperture (foramen of magendie), central canal, or lateral apertures (foramen of Luschka)
What is another name for later apertures?
Foramen of Luschka
What perfuses the brain?
Cranial Sinuses
Crainal Sinuses: Superior Sagittal Sinus
Midline
most superior
Crainal Sinuses: Inferior Sagittal Sinus
Midline
Inferior to superior sigattal sinus
Crainal Sinuses: Straight sinus
Tail end of inferior sagittal sinus
connects superior and inferior sagittal sinuses
Crainal Sinuses: Sinus Confluence
Where superior and inferior sinuses connect via straight sinus and connects with transverse sinus
Crainal Sinuses: Transverse Sinus
Lateral exit point for the straight sinus
Crainal Sinuses: Sigmoid Sinus
Makes hairpin turn
where blood flows into internal jugular vein
Crainal Sinuses: Cavernous sinus
Venous collection pool in front middle part of brain
feeds into sigmoid sinus to internal jugular vein
What is Falx cerebri?
Connective tissue between the L and R hemispheres
Also between superior and inferior sagittal sinuses
Where does the occipital lobe sit?
Tentorium cerebelli
What is inferior to the tentorium cerebelli?
Cerebellum
Where does the sigmoid sinus empty into?
Internal Jugular vein
How many jugular veins do we have on 1 side?
2- external and internal
external is small
What does the lateral apertures do?
Move CSF to the subarachnoid
What is arterial blood flow?
750 ml/min
50ml/min per 100grams of brain tissue
How much of our body weight is our brain?
2/3%
How much of our cardiac output does our brain use?
15%
How much of blood flow is for grey matter?
White matter?
80%
20%
What happens when we metabolic activity in the brain increases
Blood flow increases
Why does white matter have less blood flow?
20%
efficient at cell signaling
CSF composition: pH
7.31
The brain is carefully regulated by glial cells__________
astrocytes
CSF composition: Na+
140
CSF composition: Cl-
140
CSF composition: K+
40% LESS than plasma values
CSF composition: Mg++
Higher than plasma
CSF composition: Glucose
60mg/dL
CSF composition: color
clear
CSF composition: RBC
None
CSF composition: protein
No large amounts
CSF composition: volume
150ml
How much CFS is produced in a day?
500ml
How often is CSF replaced?
About 3 times per day
What is a chorois plexus made of?
ependymol cells
What are ependymol cells permeable to?
Na, Cl, H2O
and they have Na+ pumps and Cl- pumps
What does the ependymol cells do?
Separate CVS from CSF circulatory system
has access to blood, water, electrolytes, etc
What happens if we increase the Na in the Na+ pump in the ependymol cells?
We increase the amount of CSF produces
