Lecture 9/10: Spinal Cord and Meninges Flashcards
Exam 2
What is the purpose of the spinal meninges?
- Goal of meninges is to surround CNS with controlled environment
- Buffer/tightly regulate fluid surrounding CNS reduces potential problems
What are the 3 layers of connective tissue of the CNS?
Pia mater, arachnoid mater, and dura mater
The pia mater is the
1st layer stuck directly to neurons/glial cells
The arachnoid mater is the
2nd layer - more superficial layer to pia and large blood vessels that perfuse CNS (spinal arteries and veins - below pia, above arachnoid layer)
- fairly thin/translucent layer
What is in the subarachnoid space?
CSF and blood vessels
The dura mater is the
outer layer, tough/robust, largest
What is the subdural space? Is there anything there?
The potential space between the arachnoid and dura layers, but nothing is really there in the spinal cord
The _____ is the space immediately superficial to dural layer
epidural space
What is in the epidural space?
Adipose tissue (yellow) and venous blood vessels (blue)
Where are epidurals usually injected?
In the epidural space - shuts down AP that is being transmitted through that area of the cord
How does a lipophilic anesthetic injected as an epidural work?
Epidural space has a lot of fat, so the lipophilic anesthetics will have a longer onset because a lot is taken up by adipose, which also means it takes longer for drugs to wear off (spongy)
What are the circulatory systems for the CNS?
CV system helps perfuse CNS
CSF circulatory system - makes CSF
The ____ provides a physical cushion for the physical structures in the nervous system
CSF - helps resist damage
The majority of the CNS is made up of the _____ layer
Dura
What would be the source of a subarachnoid hemorrhage?
The blood vessels below the arachnoid mater
The ____ is the dividing point between the PNS and CNS
Spinal nerves - meninges cover up CNS or until spinal nerves
If someone is getting knee surgery and doesn’t want anesthesia, they could get an ______
epidural - shuts down motor and pain
A spinal procedure in the subarachnoid space would be ______
More risky because underneath dura and arachnoid layers - could puncture the spinal cord
Would have faster onset
The best place to do a spinal procedure is where there is no _____
spinal cord - safest in lower back
- spinal nerves can move out of the way if you go too deep, but the spinal cord can’t
Where does the spinal cord start and end?
Medulla (brainstem) → L1
What is the end of the spinal cord called?
Conus medullaris
What does cauda equina mean?
Horse’s tail
What is the cauda equina?
Where the inferior nerve roots exit the spine (posterior and anterior) - roots that haven’t yet combined to form the spinal nerves
What are the 2 enlargements in the spinal cord? Where are they located?
Cervical - upper limbs (C3-C6)
Lumbar - lower limbs (T11-L1)
The cervical enlargement feeds into the _____
Brachial plexus
The lumbar enlargement feeds into the _____
lumbar plexus and sciatic nerve
______ is the connective tissue after conus medullaris in sacral canal down to the dural sac
Filum terminale internum - red line in pic
What is the function of the filum terminale internum?
Anchors cord to structures in spine - connects cord at conus medullaris to end of dural sac
- internum = in the dural sac
What is the CSF-filled structure that extends past the conus medullaris? Where does it extend to?
The dural sac aka lumbar cistern - extends to S2, until the cauda equina exits the lower part of the spine
A good place to aim a spinal needle is
Below the conus medullaris, and dural sac
What is the connective tissue inferior to f.t. internum? What is its function?
Filum terminale externum - Ligament coming out of dural sac down to the coccyx
- Anchor that holds the bottom of the dural sac to S2
- blue line in pic
What are the anchors that keep the spinal cord from retracting up during growth?
Filum terminale internum and externum - bone grows faster than spinal cord lengthens → tension
Compare the location of the conus medullaris of an adult to a newborn
- Adult - cord ends at L1
- Newborn - cord ends at L3
What are the structures you can see in this CT?
Cervical/thoracic CT
1. Nuchal ligament
2. Supra-spinous ligament underneath fat layer
3. Cord is narrow, has black areas immediately outside of cord → CSF
4. Spinous processes angled inferiorly in T-spine
Where is a good place to get a sample of CSF? What’s the catch?
Lumbar cistern - sample isn’t fresh so take results with a grain of salt because older CSF
Circulatory system of CSF ends at the end of the cord
What are the structures you can see in this CT?
Thoracolumbar CT
1. Intervertebral discs
2. Remnants of intervertebral disc between S1 and S2
3. lumbar cistern
4. Large spinous processes but have space for needle
What are the potential access points for a CSF sample/drug administration in the lower spine?
L2-3
L3-4
L4-5
Sacral hiatus - not used frequently
Posterior sacral foramina located at S2
What angle would be “slightly off midline” for a spinal?
15-degree angle
Incomplete fusion of which ligament can make midline approach with spinal be higher risk for damaging spinal cord?
Ligmentum flavum
How does the ligmentum flavum differ in composition from the rest of spinal ligaments?
Ligmentum flavum has higher composition of elastic fibers than collagen fibers.
