Spinal Cord And Meninges Flashcards
What are the gross anatomical features/landmarks of the spinal cord?
It begins at the foramen magnum and extends down the vertebral canal until vertebral level L1/L2
How is the spinal cord divided?
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal
Describe the feature/landmark: cervical enlargement
From C4-T1 (spinal cord level, not vertebral level)
Actual spinal cord enlargement that is reflected by increased neuronal density as it supplies the upper limbs
Describe feature/landmark: lumbar enlargement
L2-S3
Spinal ROOT level
Increased neuronal density in this area as it supplies the lower limbs
What happens at C7/C8?
Above the 7th cervical vertebrae, spinal nerves exit ABOVE their respective vertebra
Below the 7th cervical vertebra spinal nerves exit BELOW their respective vertebra
C7 exits above T1 and C8 exits below T1
What is the conus medullaris?
the cone-shaped end of the spinal cord located at L1/L2 region
What is the cauda equina?
the ROOTS of the inferior spinal cord segments as they travel inferiorly in the vertebral canal t reach the appropriate intervertebral foramen level to exit
What is the filum terminale?
An extension of pia mater that arises from the conus medullaris; it passes inside the vertebral canal to fuse to the vertebral column in the region of the coccyx
What is the filum terminale?
An extension of pia mater that arises from the conus medullaris; it passes inside the vertebral canal to fuse to the vertebral column in the region of the coccyx
Describe the meninges surrounding the spinal cord from most superficial to deep
- Dura mater
- Arachnoid membrane
- Pia mater
What is the dura mater?
External outer tough covering surrounding spinal cord. Extends from foramen magnum to S2 levels of vertebral column.
Describe the dural sleeve
Dura mater that extends out along each spinal nerve to the distal end of the spinal ganglion where it becomes continuous with the epinerium of the spinal nerves
What is the dural sac?
The spinal cord ends at L1/L2, but the dura mater extends down to S1. The dura creates blind pouch called the dural sac containing the cauda equina and the filum terminale
Describe the arachnoid membrane
a vascular membrane lining inner surface of dura mater and following dura mater into dural sac
Pressure from CSF in the subarachnoid space holds the arachnoid membrane to the inner surface of the dura mater
(If arachnoid is separated from dura, something is wrong)
Describe the pia mater
The pia mater is the deepest meningeal layer and is adherent to the surface of the spinal cord (cannot be separated; piercing the pia is also piercing the spinal cord)
Describe the denticulate ligaments
Lateral extensions of the pia mater which help to anchor the spinal cord to the dura mater
Describe the filum terminale
A thin extension of the pia mater which extends from the conus medullaris to the coccyx
Describe the epidural space
Superficial to dura mater; contains fat and internal vertebral venous plexus that drains the spinal cord
Describe the subdural space
POTENTIAL SPACE: something is wrong if there is actually space here
Lies deep to the dura mater and superficial to the arachnoid membrane; contains no structures; pressure of CSF keeps arachnoid and dura together
Describe subarachnoid space
Lies deep to arachnoid membrane and contains CSF
Where is epidural anesthesia placed?
Epidural space; less effective because technically “outside” but safe because not touching spinal cord
How deep must a lumbar puncture go to collect CSF?
To subarachnoid space
(traverses dura and arachnoid)
Where does the spinal cord receive its blood supply from?
From descending longitudinal arteries
How many anterior spinal arteries are there?
ONE (an-anterior spinal artery) branched from vertebral artery
How many posterior spinal arteries are there?
TWO (I have 2 pee); branched from posterior inferior cerebellar aa.)
What are the “backup” spinal cord blood suppliers
segmental arteries to the spinal cord that branch from arteries that typically supply blood to the posterior body wall and join the longitudinal arteries
What do the anterior and posterior radicular arteries supply?
spinal nerve, dorsal, and ventral roots
What is a plexus for?
Drainage; network of veins
Describe the internal and external vertebral plexus of veins
For drainage; either internal (and inside epidural space) or external to the vertebral canal
**provide conduit for spread of cancer and infections
Where are white and grey matter, respectively, in the spinal cord?
Grey - inside; looks like butterflies; neuronal cell bodies/neurons
White - white borders grey matter; axons projecting to (sensory) and away from (motor) brain
What is the Dorsal horn (posterior horn) considered?
Sensory organ; it receives inputs from afferent fibers (blue part)
What is the ventral horn (anterior horn) of grey matter considered?
Somatic motor neurons that innervate skeletal muscles. Called “motor region.” (Green areas)
What would happen if you had a dorsal horn lesion?
Sensory loss
What would happen if you had a ventral horn lesion?
Paralysis
Where is the lateral horn?
Between the dorsal and ventral horns; evident from T1-L2 levels of the spinal cord
What are the interomediolateral (IML) cells?
Preganglionic sympathetic neurons that are always located at the levels of T1-L2; this is the outflow of sympathetic nervous system
Where are parasympathetic cell bodies located?
Between S2, S3, S4 (parasympathetic outflow)
2, 3, 4 keeps our junk off of the floor
Where are the two sets of parasympathetic preganglionic neurons located?
1/2 in S2, 3, and 4
1/2 in the brain stem associated with vagus nerve
Where is and what kind of nerve is the spinal nerve?
Ventral root - motor only
Dorsal root - sensory only
BUT spinal verve is a mixed nerve; contains both
What kind of neurons are in the dorsal root?
Pseudo unipolar (no synapse)
What kind of nerves are in the dorsal and ventral ramii?
mixed
Each spinal cord segment exhibits a ____ of spinal nerves.
Pair
Describe what happens in the spinal reflex myotonic reflex (stretch reflex).
Patellar tendon is tapped and thigh muscles are stretched briefly
Sensory fibers from a pseudounipolar neuron located in the DRG are depolarized by this stretch and activate a motor neuron in the CNS
Motor neuron fibers (multipolar) will activate the stretched muscle to prevent damage
Sensory fibers will also synapse on inter neuron (purple) in the spinal cord to inhibit antagonistic muscles
