10-15a Spinal Cord Anatomy I Flashcards
Where does the spinal begin and cord end?
foramen magnum
extends until L2
What are the cervical and lumbar enlargements on the SC due to?
more n. here where we have extremeties
Where do nerves emerging from each spinal segment go next?
leave at different levels
If someone fractures their T12 vertebra and the spinal segments there are L2/L3, where is the injury? What other spinal segments are affected?
L2/L3
all the ones below it
How many pairs of spinal nerves are there?
31
What is grey matter?
What is it divided into?
a group of cells/neurons dorsal horn (sensory neurons/connects to dorsal root) ventral horn (motor neurons/anterior horn cells)
Which grey matter horn is afferent?
dorsal horn
Which grey matter horn is efferent?
ventral/anterior horn
What other features are visible in the transversely orientated spinal segment?
white matter tracts, central canal
What varies the grey matter to white matter ratios on different leveled spinal segments?
cervical and lumbar levels: large ventral/anterior horns (cervical and lumbar enlargements = extremities)
thoracic spine: smaller anterior horns (lateral horns: SNS)
What are the white matter tracts bundled into? What comprises them?
three funiculi:
posterior funiculus:
lateral funiculus
anterior funiculus
no cell bodies: primarily axons that are either going from SC towards CNS or from CNS to SC
What are the columns/layers of cells of the grey matter called?
Rexed’s laminae
What is the gradient along Rexed’s laminae
dorsal: n. that receive sensory input (ex. lamina 1 and 2 pain fibers, 3 and 4 mechanoreceptor)
middle: integration b/w sensory input and motor output (5 and 6)
ventral: anterior horn cells/motor n. (9 and 10: anterior horn cells/somatic n.)
Where do the dorsal and ventral nerve roots join? Sensory or motor?
spinal root/spinal nerve
mixed
What does the dorsal ramus supply?
mixed n. of the muscles and skin of the back
what does the ventral ramus supply?
mixed n. that forms a part of the plexi (brachial and lumbosacral plexus that supplies UE and LE) and visceral organs
Where is the brachial plexus?
C5-T1
Where is the lumbar plexus?
L1-L4
Where is the sacral plexus?
L5-S4
What are axons surrounded by?
Schwann cells
What is the outermost CT layer of the spinal n?
epineurium
What are the different divisions of the brachial plexus?
five roots (ventral rami) three trunks six divisions three cords five branches
What is are the axons and * coated by?
endoneurium
What are bundles of axons grouped into?
fasicle
What are each bundle of axons coated by?
perineurium
What are the bundles of axons coated by?
epineurium
What is the path of the sensory component to a peripheral spinal nerve to the SC?
dorsal root < sensory axons and cell bodies in DRG < spinal nerve < dorsal or ventral ramus < sensory n. receptors (free nerve endings of sensory n.)
are the dorsal/ventral roots mixed?
no
What can the functional anatomy be categorized into?
sensory and motor organization
Where are the cell bodies for sensory axons
DRG
what composes the sensory org?
peripheral sensory organs
affarent/sensory axons whose cell bodies are in DRG, which goes into the SC > synapses at level of SC or it goes up to CNS
what composes the motor org?
n. in anterior horn (anterior horn cells) > exit through ventral root > pass through plexus > supplies m. fibers
what is the sensory component of the peripheral n?
receptor > sensory afferent n. > DRG no synapse here bipolar neuron: one axon goes to peripheral receptor and the other goes to CNS
What are the three pathways once the sensory afferent n. reaches spinal cord?
- relays info at the level it enters and innervates that n. center
- goes up to the somatosensory cortex
- synapses to other segments of the SC
Where do the spinal motor n. sit?
anterior horn cells
What are the characteristics of the anterior horn cells?
- Final common motor output
- Three types: Alpha, Beta and Gamma
- Axons of AHC are myelinated
- Organized in columns in the anterior grey matter of the spinal cord
what is a motor unit?
the neuron and all the m. fibers it innervates
All muscles in motor unit contract together when neuron fires : ALL OR NONE LAW