www.thinkback.ca - What is the spine?

www.thinkback.ca > what is the spine?

The spine does three (3) main things in our body:

Moves - it allows us to bend in performing daily activities.
Support - it allows us to stand upright and carry our body weight throughout the day.
Protects - it protects our spinal cord and nerves so they do not get damaged.

The spine does these three things on a daily basis; however, it is sometimes difficult to provide a large amount of movement while still protecting and supporting - or vice versa.

The spine is made up of 33 bones stacked one on top of the other, creating 4 curves. What you think of as your hipbones (or pelvis) is attached to the spine at the tailbone.

By clicking the different areas of the graphic (on the right), you will see a 3D view of the following 4 areas of the spine:	figure 1 - roll mouse over spine to view different regions. Click for 3D view.
Neck (Cervical) - is made up of 7 bones and they are the smallest and lightest in the spine. Upper Back (Thoracic) - is made up of 12 bones that connect with the ribs. Lower Back (Lumbar) - is made up of 5 bones that are larger and heavier than the neck and upper back bones. Tailbone (Sacrum/Coccyx) - is made up of 9 bones that are fused together.
	** Please note that this is a general representation of the spine and is not meant to show its exact structure

The bones of the spine are called vertebrae (See figure 2a and 2b).

figure 2a

Lumbar vertebra (left side view)

figure 2b

Lumbar vertebra (top view)

A disc sits between each pair of vertebrae and allows for movement in the spine. The disc is composed of a tough outter ring and a softer inner core. The tough outer core is constructed much like a radial tire, with many fibres crossing to increase its strength and durability. (See figure 3a) The inner core is a jelly-like substance with a harder ball, or a nucleus at its center. (See figure 3b) The disc is what allows for movement of the spine, with the ball bearing (nucleus) acting as a pivot point for the vertebrae to move one on top of another.

figure 3a - vertebral disc (side view)

figure 3b - vertebral disc (top view)

Each vertebral segment, vertebra and disc, (See figure 4) allows for movement forward, backward, twisting and to the side.

figure 4a - roll mouse over below

twisting movement

figure 4b - roll mouse over below

forward & backward movement

figure 4c - roll mouse over below

side bending movement

The muscles of the spine act as guy wires supporting the spine and making it stable (think of it like the wires that hold up the mast of a ship). If the “wires” are strong and balanced on all sides then the spine will be supported and stabilized. If, however, the “wires” are weak and not balanced the spine will not be supported or stabilized. This instability could lead to excess stress on the spine and eventual injury.