M1 Reading Guide Flashcards
What is the function of the curves in the spinal column (or, why is a curved spine better than a straight spine)?
- contributes to ideal spinal posture in standing
- reduces compressive load
What do anterior concavities provide?
space for organs in the thoracic and pelvic cavities
What is the primary WB component of the spinal column?
intervertebral discs
Lumbar vertebral bodies function
- load bearing
- not designed to absorb 100% of the weight
Curves of the spine help minimize _______
compressive load
In addition to lumbar vertebral bodies and discs, what else help absorb a small amount of load?
facet joints
What type of joints are facets?
synovial
What is true of all synovial joints?
- mobile
- surrounded by pliable capsule
SI joint starts out as this type of joint
synovial during childhood
What type of joint does the SI become?
- modified diarthroidal synovial joint between puberty and adulthood
- » modified synarthroidal joint in adulthood
Where do synovial joints get nutrition?
synovial fluid
Are synovial joints sources of pain? Why or why not?
YES - highly innervated
In what way does the facet joint capsule act as a ligament?
- limits motion at the interbody joint
- » supports and protects interbody joint and disc
How are spinal motions distributed L1-L4?
- mostly vertical
- mostly sagittal plane
- allows a lot of flexion/extension
- doesn’t allow much rotation
This serves to guide and limit motion in the lumbar spine
orientation of facet joints (?)
Position of facet joints L5-S1
Change from vertical to a more oblique position between frontal and sagittal plane
What function does a more oblique position of facets at L5/S1 serve?
resist anterior shear created by sacral angle of inclination
What do shear and facet compression increase with?
- increased lordosis and/or
- increased angle of inclination
What does the increased obliquity of the L5/S1 facets limit? (movements)
- lateral flexion
- rotation
Gravity imposes a much higher degree of _______ force at L5-S1 than the rest of the lumbar spine
shear force
What is the angle of inclination?
angle that the sacrum is tipped forward
What is the shear force that goes through the L5-S1 joint? (%)
50%
If a person has 90# force directed through the spine, 45# is directed through this junction
