M1 Reading Guide 4 Flashcards
What are the two types of bone in a vertebra?
- compact (cortical)
- trabecular (spongy/cancellous)
compact bone withstands
greater stress
trabecular bone withstands
compression
What happens to trabecular bone in response to stress?
hypertrophy
What happens to trabecular bone in the absence of loading?
- becomes smaller and weaker
- osteoporosis
In standing or forward trunk flexion of the lumbar spine, what does the pars interarticularis resist?
shearing forces
In standing or forward trunk flexion of the lumbar spine, when is the pars interarticularis most likely to fail?
repetitive loading with:
- flexion
- extension
especially at end range
Most common level of pars interarticularis failure
L5-S1
Unilateral failure or lengthening of the pars interarticularis =
spondylolysis
bilateral failure or lengthening of the pars interarticularis =
spondylolysthesis
If the pars fails or lengthens bilaterally, what is likely to occur subsequently between the two adjacent segments?
anterior slippage of top vertebra over the vertebra below it
What are the two main functions of the annulus fibrosis?
check for accuracy
- encase/physically entrap the liquid based central nucleus
- absorb shock and load, allow/restrict movement
Outer peripheral rings of the annulus contain
blood vessels
Inner layers of the annulus contain
less type I collagen and more water
What is the consistency of the nucleus pulposus?
pulp-like gel
