Spinal Cord Flashcards
What is the conus medullaris?
Terminal point of the spinal cord @ ~L1-L2
What are the meningeal coverings of the SC
Brown - dura mater
Green = arachnoid mater
Red = pia mater
Describe the spaces in the SC
Red = epidural space (fat and venous plexus)
Yellow = subarachnoid space (CSF and spinal blood vessels)
What are denticulate ligaments
Thickening of pia and glial elements that form ribbons along lateral surface of SC
What is the filum terminalae
Extension of pia and supporting cells that connects the conus medullaris to the coccyx bone
Label the following
Posterior (posterolateral sulcus) – where sensory info enters
Posterior median fissure
Anterolateral sulcus – where motor info exits
Anterior median fissure
Differences between SC sections at cervical, thoracic and lumbar segments?
- Cervical and lumbar have the most grey matter because they innervate the limbs
- Cervical white matter > thoracic > lumbar because motor information from all spinal segments is carried at the most caudal sections
Two sources of spinal cord blood supply
- Vertebral basilar system
* PICAs and vertebral arteries join to form the posterior spinal artery and anterior spinal artery - Segmental arteries
- Posterior brances of intercostal arteries give rise to segmental spinal arteries
- Segmental spinal arteries branch to form either (a) radicular arteries that supply roots at each level of SC or (b) segmental medullary arteries which supply either the PSA or the ASA
- Segmental p
Where do segmental spinal arteries originate
Anterior intercostal arteries
What originates from segmental spinal arteries
1) Radicular arteries (supplies roots)
2) Segmental medullary arteries (supply the ASA or the PSA)
Describe the blood supply from the ASA and PSA to the SC
- The ASA supplies the anterior 2 thirds of the SC, including the base of the posterior horns
- The PSAs supply the posterior 1/3 of the SC
What is the composition of a spinal nerve
1) Sensory root (afferent) to posterolateral sulcus
2) Motor root (efferent) exiting from anterolateral sulcus
Number of cervical vertebrae and nerves
CI - CVII (7 vertebrae)
C1-C8 (8 nerves)
Number of thoracic nerves and vertebrae
TI - TXII (12 vertebrae)
T1-T12 (12 nerves)
Number of lumbar nerves and vertebrae
LI-LV (5 vertebrae)
L1-L5 (5 nerves)
Number of Sacral nerves and vertebrae
5 vertebrae fused as sacrum
5 nerves (S1-S5)
Number of Coccygeal nerves and vertebrae
1-4 coccygeal vertebrae (fused as coccyx)
1 nerve (C0)
Where are the sympathetic nervous system efferents in the SC?
T1-L2 segments; cell bodies are in LATERAL HORNS in thoracic cross-sections
Where are the parasympathetic visceral efferents in the SC?
S2-S4
Where are the SC enlargements?
- Cervical: C4/5 - T1
- Lumbosaral: L2-S3
What is visible in a SC cross-section from T1-L2/3?
Lateral horn (intermediolateral cell column)
-contain preganglionic sympathetic cell bodies
What is visible in a SC cross-section at S2-S4
Lateral horn
Preganglioic parasympathetic cell bodies
What type of information is carried by General Somatic Afferents (GSAs)
- Discriminative Touch
- Proprioception
- Somatic pain and temperature
What type of information is carried by General Visceral Afferents?
- Sensation from the viscera
What type of information is carried by General Somatic Efferents?
- motor to skeletal muscles
What type of info is carried by General Visceral efferents
Motor to viscera
- Originates in lateral horns, exits via the anterolateral sulcus, travels through motor roots to spinal nerve
Interomediolateral nucleus
Cell bodies of visceral motor efferents found only in T1-L2 (SYMPATHETIC) and S2-S4 (parasympathetic efferents)
Where are parasympathetic motor (efferent) nerves found?
- Cranial nerves 9-12
- S2-S4 of spinal cord
Which laminae are present in the dorsal (posterior) horns?
Rexed laminae I - VI:
I = Posterior (dorsal) root fibers mediating pain, temperature, and touch; posteromarglnal nucleus
II: Subatantla gelatinosa neurons mediating pain transmission
III and IV: Proper sensory nucleus receiving Inputs from substantla gelatinosa and contributing to anterolateral system
V: Neurons receiving afferent Input from vlscera, skin, and muscle
VI: (only in cervical): afferents from muscle spindles
Which nuclei are present in dorsal horns?
1) substantia gelatinosa
2) nucleus propius
3) dorsal nucleus of clarke
Function of Lissauer tract (posterolateral fasciculus)
Sensory fibers carrying pain and temperature will ascend or descend several spinal cord levels here before synapsing In the dorasal horn.
Path of sensory fibres containing discriminative touch and proprioceptive info
1) Enter through posterior horn (posterolateral sulcus)
2) Ascend in ipsilateral (same side) dorsal/posterior columns (e.g., fasciculus gracilis, fasciculus cuneatus)
Path of sensory fibres containing PAIN information
- Enter dorsal horn
- travel up/down 1-2 segments in Lissauer tract
- Modulation in substantia gelatinosa/Rexed laminae 2
- synapse in nucleus proprius
- Decussate via anterior commissure and travel in the contralateral spinothalamic tract
Path of alpha motor neurons
Exit anterior (ventral) horn and travel to muscles
Path of Ia, Ib, and II fibres carrying proprioceptive information (destination = cerebellum)
- Enter via dorsal horn
- Synapse at Dorsal nucleus of Clark if L3-C8
- Travel in ipsilateral spinocerebellar column
- If below L3, travel in fasciculus gracilis then synapse in Clarke Nucleus
- If above C8, travel in fasciculus cuneatus and synapse in the accessory cuneate nucleus
- Then travel in cuneocerebellar track to cerebellum
What travels in the anterior corticospinal tract
- UMNs concerned with proximal trunk musculature (ipsilateral)
- Cross over in appropriate level of spinal cord
What travels in lateral corticospinal tract
UMNs to ipsilateral (same side) anterior horn
Mostly for limb musculature
Somatotopic (cervical musculature is most medial, sacral most lateral)
