Spine Anatomy

Spine Anatomy

The spinal column, which is a series of bones that supports the body, maintains posture, and protects the spinal cord and nerves, is divided into several main sections:

Cervical (neck)

Thoracic (chest)

Lumbar (low back)

Sacrum (base of the spine, incorporated into the pelvis)

Coccyx (tailbone)

Each bone of the spine has similar features. In the front part of the spinal bone is the vertebral body (here marked "Vertebra"). Between the vertebral bodies are the intervertebral discs. Behind the disc at each level, a nerve root exits in a space called the foramen. Behind the foramen is a joint called the facet joint.

To see about narrowed formen, click here.

The disc, which is a cushion between the vertebral bodies, has a structure like a jelly donut, with a center (nucleus pulposus) with higher water content and an outer ring that would be more like the dough (annulus fibrosus). With this structure, the disc provides a cushion between the bones, but is also flexible. To see more about back pain, click here.

In the back part of the spine, there are joints that are in contact with the corresponding joints of the vertebra above and below. These joints are called the facet joints. These joints are covered with the type of cartilage like on the end of a chicken bone. This joint surface, which is normally smooth, can with wear and tear, become arthritic and rough, and be a source of pain.

To see a model with normal appearing facets, click here.

To see worn out facets, click here.

Behind the body is the place where the spinal cord and nerves reside, an area called the spinal canal.

For each spine bone (vertebra), there is a facet that goes upwards (the superior facet) and one that goes downward (the inferior facet). The part in between these facet joints, which is an important landmark, is called the pars interarticularis.

The bones in the neck have a little different shape, but the same elements, disc in front, facets in back, nerve root leaving at every level, are still there.

For a video on cervical spine motion (found on youtube.com), click here.

One detail regarding MRI pictures:

For the cuts that are taken across the long axis of the spine, like slicing a salami, the cuts will be either (A) through the pedicle, which is the tube of bone that connects the body in front with the lamina and facets in back, or

(B) through the foramen, which are the holes through which the nerve roots exit (B).

For a more expansive explanation from the website

Mark A. Wolgin, MD Orthopaedic Surgeon

Specialist (Fellowship Trained) in Spinal and Foot/Ankle Surgery