|
The spine is a column of 26 bones that extend in a line from the base of the
skull to the pelvis (see fig. 1). Twenty-four of the bones are called vertebrae.
The bones of the spine include 7 cervical vertebrae in the neck; 12 thoracic
vertebrae at the back wall of the chest; 5 lumbar vertebrae at the inward curve
(small) of the lower back; the
sacrum, composed of 5 fused vertebrae between the
hip bones; and the coccyx, composed of 3 to 5 fused bones at the lower tip of
the vertebral column. The vertebrae link to each other and are cushioned by
shock-absorbing disks that lie between them.
The vertebral column provides the main support for the upper body, allowing
humans to stand upright or bend and twist, and it protects the spinal cord from
injury. Following are structures of the spine most involved in spinal stenosis.
Intervertebral disks – pads of cartilage between vertebrae that act as
shock absorbers.
Facet joints joints located on both sides and on the top and bottom of
each vertebra. They connect the vertebrae to each other and permit back motion.
Intervertebral foramen (also called neural foramen) - an opening between
vertebrae through which nerves leave the spine and extend to other parts of the
body.
Lamina - part of the vertebra at the upper portion of the vertebral arch
that forms the roof of the canal through which the spinal cord and nerve roots
pass.
Ligaments - elastic bands of tissue that support the spine by preventing
the vertebrae from slipping out of line as the spine moves. A large ligament
often involved in spinal stenosis is the ligamentum flavum, which runs as a
continuous band from lamina to lamina in the spine.
Pedicles - narrow stem-like structures on the vertebrae that form the
walls of the bottom part of the vertebral arch.
Spinal cord/nerve roots - a major part of the central nervous system that
extends from the base of the brain down to the
lower back and that is encased by the vertebral column. It consists of nerve
cells and bundles of nerves. The cord connects the brain to all parts of the
body via 31 pairs of nerves that branch out from the cord and leave the spine
between vertebrae (see fig. 2).
Synovium - a thin membrane that produces fluid to lubricate the facet
joints, allowing them to move easily.
Vertebral arch - a circle of bone around the canal through which the
spinal cord passes. It is composed of a floor at the back of the vertebra, walls
(the pedicles), and a ceiling where two laminae join.
Back to Spinal Stenosis |
