Lumbar Spine Anatomy & Definitions Flashcards
trabeculae
- cancellous or spongy bone
- stabilizes longitudinal loads
- advantage: solid structures are not ideal for dynamic load bearing/solid.
vertebral body
the thick oval segment of bone forming the front of the vertebra also called the centrum. The cavity of the vertebral body consists of cancellous bone tissue and is encircled by a protective layer of compact bone
pedicles
two thick pillars of bone that project post/lat. from the upper part of the back of the vertebral body; transmits forces
posterior elements of the vertebral body
- laminae
- pars interarticular processes
- spinous processes
- transverse processes
- mammillary process
- site of muscular attachment
laminae
bony protective covering over neural contents of vertebral canal; absorbs forces from spinous & articular processes.
-stability of the lumbar spine can be compromised when a lamina is destroyed or weakened by disease, injury, or surgery
pars interarticularis
- connects vertically oriented lamina & horizontally extending pedicle
- subject to considerable bending forces as the forces transmitted by the lamina undergo a change of direction into the pedicle
- cortical bone in this area thicker than anywhere else in the lamina
mammillary process
- multifidi muscle attaches
- helps stabilize the vertebral joints
What percent of the nucleus pulposus is water?
85%
What percent of the nucleus pulposus is collagen?
15-20% chondroblasts
What type of collagen is produced in the nucleus pulposus?
type II - resisting compression
What percent of the nucleus pulposus is proteoglycans?
65% of dry weight
What are the effects on the nucleus pulposus with aging?
- water goes from 85% to 70%
- increased type I collagen fibers (type II collagen is produced normally)
- decrease in proteoglycans
- decrease aggregates & decreased capacity for osmosis
What percent of the anulus fibrosus is water?
60-70%
What percent of the annulus fibrosus is collagen?
50-60% of the dry weight (arranged in a highly ordered pattern, type I most dominant resisting tensile forces)
What percent of the annulus fibrosus is proteoglycans?
20% of dry weight
What are the effects on the annulus fibrosus with aging?
- reduction of water from 60/70% to 50%
- increase in type III collagen fibers (type I is normally most dominant)
- decrease in proteoglycans
lamellae
-sheets that are arranged in concentric rings that surround the nucleus pulposus. thicker towards the center of the disc, thick in the ant/lat portions of the annulus, but posteriorly they are finer & more tightly packed
How are the collagen fibers oriented diagonally?
-alternate successive lamellae
How are the collagen fibers oriented vertically?
-always the same, 60 degrees
What is the advantage of the collagen fibers in the intervertebral disc being oriented vertically and diagonally?
-each fiber can offer a component of resistance both vertically & horizontally which allows it to resist movements in all directions
What is the sensory innervation for the intervertebral disc?
-sinuvertebral nerve off of the anterior primary rami
What is the function of the IVD?
-the disc allows movement between the vertebral bodies by transmitting loads from one vertebral body to the next
If a weight is applied to a disc, how do it’s volume and shape react?
-the disc can become deformed but it’s volume cannot be compressed
blood supply of the IVD
nonexistent