spinal cord divisions

cervical: 8

thoracic: 12

lumbar: 5

sacral: 5

coccygeal: 1

spinal enlargements

cervical and lumbar

where do the cervical spine nerves exit?

above the corresponding vertebrae but C8 comes below C7

where do the rest of spinal nerves exit from?

below the corresponding vertebra

growth of spinal cord @ birth

level of the third lumbar vertebra

how does the spinal cord grow through childhood?

body and spinal column grow more than the spinal cord

where does the adult spinal cord end?

at the level of the disk between L1 and L2

length of spinal nerves

progressively longer as it continues from cervical to coccygeal segments

where does the dural sheath extend?

level of S2

lumbar cistern

space between the end of the cord and the end of the dural sheath

what is located in the lumbar cistern?

ventral and dorsal roots

what do the ventral and dorsal roots make up?

cauda equina

subarachnoid space

space between pia mater and arachnoid that is filled with CSF

epidural space

between dura and bones of vertebral column

grooves of the spinal cord

posterior median sulcus, anterior median fissure, posteriolateral septum, and anteriolateral fissure

posterior median sulcus

midline grooves in posterior white column

anterior median fissure

midline grooves in anterior aspects

largest groove in spinal cord

posteriolateral septum

dorsal root enters the spinal cord

anteriolateral fissure

ventral root exits the spinal cord

conus medularis

terminal end of the spinal cord (L1-2)

cauda equina

located below the conus medularis (L3-5) and contains peripheral nerve fibers that innervate the LE

filum terminale

tapered thin filament that comes from the end of the conus medularis and runs through the cauda equina

pia mater and neuroglia

how are the ten divisions in gray matter of the spinal cord numbered?

from dorsal to ventral

lamina I

most dorsal layer of gray matter and contains small cells and receives dorsal root fibers

sends axons to contralateral spinothalamic tract

lamina II

also named substantia gelatinosa since it contains gelatinosa cells with highly branched dendrites.

receives dorsal root axon and descending fibers from reticular formation and is a modulator for pain sensation

laminae II

contains interneurons that interconnect with other dorsal horn laminae

lamina IV

cells for ascending tracts that have long dendrites that connect lamina II and III

origin of the spinothalamic tract and receives most of the dorsal root

what laminae receives dorsal roots?

I-IV

laminae V-VI

located at the base of dorsal horn and is indistinguishable in humans

cells also provide spinothalamic tracts

laminae VII

intermediate zone with the largest region of gray matter

contains the nucleus dorsalis (clarke’s column), intermediolateral cells (sympathetic preganglionic), and sacral parasympathetic preganglionic cells

lamina VIII

ventral horn and contains motor neurons and some interneurons

receives nerve fibers from descending tracts (vestibulospinal and reticulospinal) and communicates with laminae VII and IX

lamina IX

columns of motor neurons (alpha and gamma)

lamina X

located immediately around central canal and contains crossing fibers and glial cells

internal structure of spinal cord

central area: gray matter

outer: white matter

gray matter

comprised of nerve cell bodies

white matter

consists of nerve fibers or tracts

primary sensory afferents

cell bodies in the dorsal root ganglia and is located proximally to the junction of the dorsal and ventral roots

primary afferents synapses

enter spinal cord and synapse within the dorsal horn on the second order neurons or interneurons

also synapse in the ventral horn on motor neurons and contribute to the spinal reflexes such as deep tendon reflexes (knee jerk)

ventral horn composition

alpha and gamma motor neurons and interneurons

lateral, ventral horn neuron innervation

distal limb musculature associated with joint movement

medial, ventral horn neuron innervation

proximal and axial muscles associated w postural control and stability

intermediolateral cell column

region from T1-L2/3 located between the dorsal and ventral horns

intermediolateral cell column neurons

preganglionic sympathetic neurons

how is the white matter divided?

anatomically and functionally

anatomical division of white matter

the spinal cord white matter is divided into funiculi: dorsal, lateral, and ventral

funiculi composition

long ascending fibers and long descending fibers

long ascending fibers of funiculi

convey sensory information from body to the thalamus, cerebellum, and various brainstem nuclei

found in all three funiculi

long descending fibers of funiculi

originating in the cerebral cortex or brainstem and found in the lateral and ventral funiculi

how the axon fibers run in white matter? what do they form?

longitudinally and project together to from various tracts of the spinal cord

dorsal funiculis - what do these fibers carry?

conscious proprioception, kinesthesia, discriminative touch sensation, and vibration

cuneocerebellar tracts

one of the four spinocerebellar that carry unconscious proprioception from the UE

lateral funiculis

contains both sensory and motor tracts

sensory/ascending tracts of the lateral funiculis

lateral spinothalamic, spinocerebellar, spinotectal

lateral spinothalamic sensation

pain and temperature

spinocerebellar sensation

unconscious proprioception

motor/descending tracts of the lateral funiculis

lateral corticospinal and rubrospinal

lateral corticospinal function

motor control for distal limb movements

rubrospinal function

distal limb movement

tracts of the ventral funiculis

ascending: anterior spinothalamic tract

descending: ventral corticospinal and vestibulospinal tracts

anterior spinothalamic tract

carry light touch sensation

ventral corticospinal tracts

facilitate postural control and balance correction

vestibulospinal tracts

control balance