This week's question: How do you get your glow...
14 minutes ago
By Stan Andrzejewski • January 27th, 2006 • 8626 Views
The human spine is a segmental structure, consisting of 7 cervical, 12 thoracic, 5 lumbar, 5 sacral [fused], and 4 coccygeal [fused] vertebrae. Of course, the sacral and coccygeal "vertebrae" are considered part of the pelvic girdle as sacrum and coccyx.
A basic vertebra is comprised of a bony block and a bony ring. The block is sandwiched between spinal disks. The ring houses the precious spinal cord. The ring consists of 2 pedicles, 2 lamina, 1 spinous process, and 2 transverse processes. Processes are levers that attach to muscles. Each vertebra has 4 facets [joints], 2 superior, 2 inferior attached on the lateral posterior side of the vertebral body. A thoracic vertebra has 4 more facets attaching to the ribs. The angle of orientation of the facets changes with each level of vertebra. The facet angle influences the direction of movement.
Much can be told of function by the structure itself.
Lumbar vertebrae are massive for weight bearing. The facets have a sagittal orientation allowing little rotation, but a lot of flexion, extension.
Thoracic vertebrae are smaller than lumbar, larger than cervical vertebrae. We have 4 more demi-facets per vertebrae to attach our ribs. These are more facets to become hypomobile and restrict spinal movement. Ribs are the armor of our vital organs. The spinous processes are sharply angled down to prevent excessive backbending.
Cervical vertebrae are the smallest, designed for mobility of our head. Facets are angled at 45 degrees from the horizontal for the most range of motion..
The spine is a load bearing structure. It is designed to carry the weight in a tripod configuration. The disks bear weight in the front and the facet joints bear the weight in the back. The lumbar disks are massive, in compassion to the other disks, and are designed to bear 80% of the weight [facets: 20%]. The cervical disks, much smaller, are designed to carry 50% of the weight [facets: 50%].
We can consider that, normally, each vertebra can move in all directions. The manual therapist and the yogi use the image of the vertebra floating [or stuck] in any direction. We categorize each vertebra movement as flexion [nutation], extension [counter-nutation], rotation, and side bending. Some vertebras are restricted more than others. This is called the relative flexibilities/inflexibilities of the spine....