spinal cord: structural and functional organization

vertebrae

bones that make up the vertebral column, which is a casing that protects the spinal cord

32

number of vertebrae bones that make up the vertebral column

cervical

7 bones make up this segment of the vertebral column

thoracic

12 bones that make up this segment of the vertebral column

lumbar

5 bones that make up this part of the vertebral column

sacral

5 fused bones that make up this part of the vertebral column

coccyx (1)

3 fused bones that make up this part of the vertebral column (1)

laminectomy

removal of the roof of the vertebral canal to expose the underlying spinal cord

body

transverse process

spinous process

lamina

connect the transverse processes with the spinous process

vertebral canal

spinal cord is located here

intervertebral foramen

joint between two vertebrae; site where nerves going out to muscles or carrying sensory information into spinal canal emerge

dorsal root ganglia

contain neuronal cell bodies that are involved in carrying sensory information from the periphery to the spinal cord

spinal nerve

the dorsal and ventral roots unite to form this, which continous out to the periphery - contain both sensory and motor information

dorsal horn

dorsal rootlets

dorsal root

transmit sensory information from the periphery to the CNS

ventral horn

ventral rootlets

ventral root

carry motor information from the CNS to the periphery

meninges

membrane that surrounds the central nervous system; composed of three layers

dura mater

arachnoid

pia mater

layers of meninges (first - outermost; last - innermost)

dura mater

tough mother; thick/dense membrane of the meninges

arachnoid

the middle layer of the meninges, the outersurface attaches to the dura mater, its characteristic meshwork extends to pia mater

pia mater

tender mother; adheres to all surfaces of the CNS

subarachnoid space

located between the arachnoid and pia mater; contains the cerebrospinal fluid

coccyx

where all three layers of the meninges terminate

2nd lumbar vertebrae

where the spinal cord ends in an adult; level of the spinal cord is not the same as their adjacent vertebral level

embryo 8 weeks

all three layers of meninges anchored to coccyx

spinal cord extends from base of skull to coccyx

nerves leave the spinal cord through adjacent intervertebral foramen

embryo 24 weeks

all three layers of meninges anchored to coccyx

spinal cord extends from base of skull to S-1 (sacral-1)

nerves still leave through the same foramne as E-8weeks, however they have stretch to reach out

birth

all three layers of meninges anchored to coccyx

spinal cord extends from skull to lumbar-3

nerves leave through the same foramen as E-8weeks, they stretch to reach it

adult

all 3 layers of meninges anchored to coccyx

spinal cord extends from skull to L-2

nerves leave through the same foramen as E-8weeks, they stretch to reach it

filum terminale

fine filament that extends inferiorly from the distal end of the spinal cord; it is made up of pia-mater (non-neural tissue) - extends from conus medullaris

cerebrospinal fluid

located in the subarachnoid space between arachnoid and pia mater - forms a reservoir below the distal end of the spinal cord

lumbar puncture

carried out to collect samples of CSF for testing or for injection of anesthesia into CSF for spinal block

• needle inserted below L3 to avoid contact with SC

conus medullaris

tapered distal end of the spinal cord

cauda equina

made up for ventral and dorsal roots arising from the spinal cord and descending to their respective intervertebral foramen to exit at lower lumbar and sacral levels

cauda equina syndrome

caused by tumor or rupture of intervertral disk that encroaches on cauda equina in vertebral canal

• treated with surgical decompression to avoid permanent damage

• saddle numbness

nissl stain

label endoplasmic reticulum in cell bodies

fiber stain

labels myelin on axons

butterfly

center of the spinal cord; contains neurons and glia (grey matter)

grey matter

primarily made up of neurons (cell bodies)

white matter

primarily made up of myelinated axons

intermediate gray area

located between the dorsal and ventral horn; primarily used by autonomic nervous system

tract

a bundle of axons arising from a specific area and having the same function; connect two CNS regions

ascending tract

project from the spinal cord to the brain

descending tract

project from the brain to the spinal cord

fasiculus

a bundle of anatomically defined fibers that serve a common function (aka tract)

funiculus

an area containing multiple tracts

dorsal column/funiculus

white matter located in between dorsal horns; contain multiple tracts

• sensory information (ascending)

• contains large diameter processes of dorsal root ganglia

ventral column/funiculus

white matter located between two ventral horns; contain multiple tracts

• motor informsation (descending)

lateral funiculus

between lateral edge of dorsal and ventral horns; contains multple tracts

• sensory and motor tracts

• ascending and descending tracts

anterior white commissure

located dorsal to the anterior median fissure

• contains axons from one side of spinal cord to another