Philosophical Heritage
"I profess both to learn and to teach anatomy, not from books but from dissections; not from positions of philosophers but from the fabric of nature."

- William Harvey 1578-1657

Nature's Design
Anatomy is the underlying structure, and like any building is constructed with a certain consistency and a tolerance for minor variations. A range of normal exists and a range of abnormal (pathologic). Nature has made the design decision, tested it, re-worked the flaws and determined the acceptable construct. But design is not always perfectly executed, and errors emerge. The basic building of nature is subjected to the wear and tear of time, and is persuaded by the forces of daily life into accommodation. Within these dynamic mechanical swings, the building withstands the challenge, or weakens slightly or collapses on its foundation. The surgeon's work can never be as perfect as nature's, but patching up the building can leave it standing and functional. The seven wonders of the world are all man made: the greatest wonder is not.

View the Spine Anatomy animation here.

Normal Anatomy
Lateral (side) view of a normal spine. The drawing shows the locations of the five major spinal levels. The cervical region has seven vertebrae (C1 through C7), the thoracic region has 12 vertebrae (T1 through T12) and the lumbar region has five vertebrae (L1 through L5). The sacral region consists of five vertebrae, all fused together to form one continuous bone mass known as the sacrum.

The coccygeal region consists of four vertebrae, all fused together to form the coccyx or tailbone.

Detailed views of a vertebra and vertebral segment.
The drawing above represents a top view of a lumbar vertebra. The drawing below is a lateral (side) view of a segment of three lumbar vertebrae.

Reprinted with permission from Metronic Sofamor Danek

The drawings above and below represent the appearance of a herniated or ruptured disc. Both drawings show the disruption of the annulus fibrosus, the outer ring-like portion of an intervertebral disc.

The tissue located in the center of the intervertebral disc, the nucleus pulposus, is partially extruded from the intervertebral disc. The extruded nucleus pulposus material can exert pressure on nerves thus causing pain, numbness, and muscle weakness due to nerve damage.

An abnormal spinal condition known as scoliosis is shown in this drawing. Scoliosis is a lateral (sideways) curvature of the spine.

Spondylolisthesis is an abnormal spinal condition in which one vertebra slips or is displaced over another vertebra. The drawing shows spondylolisthesis as a result of a lumbar vertebra (L5) slipping over the sacrum (S1).

This drawing depicts the spinal condition of kyphosis. Kyphosis is an abnormal increase in normal kyphotic (posterior) curvature of the thoracic spine which can result in a noticeable round back deformity.

This drawing represents the spinal condition of lordosis. Lordosis is the abnormal increase in normal lordotic (anterior) curvature of the lumbar spine. This can lead to a noticeable "sway-back" appearance.

This drawing illustrates degenerative and hypertrophic arthritis between the 3rd, 4th, and 5th lumbar vertebrae, as well as the lumbosacral joint (L5-S1 disc space). The degeneration of the intervertebral discs has reduced the height of the discs. There are bone spurs or hypertrophic bone adjacent to the discs and hypertrophic arthritis of the facet joints. This results in reduced range of motion of the spine. Also, the hypertrophic bone and narrowing of the intervertebral foramen can produce nerve root impingement thereby causing back and leg pain, as well as numbness and weakness of leg muscles.

Republishes with permission from Medtronic Sofamor Danek