Spine Basics
Your spine consists of all the bones, discs and nerves from the top of your neck to your tailbone. The spine has a bone column and a nerve column. The spine is divided into five different areas. Each of these areas has a curve and a different number of bones (vertebrae) as listed:

1) Cervical Spine (Neck)
The cervical spine is made up of seven bones (vertebrae). They start at the base of your skull and go down to about the top of your shoulders. The bones in your neck are numbered one through seven. When we refer to them, we use the letter "C" along with the vertebrae number because the bones are in the cervical spine. So the top bone in the neck is called "C1" and the bottom bone is called "C7."

2) Thoracic Spine (Upper Back)
Below the cervical spine (neck) there are twelve vertebrae that make up the thoracic spine. This is sometimes called the dorsal spine. Attached to the sides of each vertebra in the thoracicspine are ribs. The vertebrae in the thoracic (dorsal) spine are referred to using the letter "T" or "D" along with the number of the vertebra in the thoracic spine (1-12).

3) Lumbar Spine (Low Back)
The lumbar spine (low back) is made up of five vertebrae (bones). We use the letter "L" when we talk about the bones of the lumbar spine. The lumbar spine starts just below the ribs and ends at the top of your buttocks. This is the portion of the spine where people have the most trouble. Most people who have reached the age of 60 have had a low back ache at one time or another

4) Sacrum
Below the lumbar spine are five vertebrae that are fused (joined) together. These form the sacrum in the back of the pelvis. We refer to these vertebrae using the letter "S" for sacrum.

5) Coccyx (Tailbone)
Below the sacrum is a small bone called the "coccyx." Sometimes during a fall you can bruise this small bone. Some women will have tenderness in this bone after having a baby. It is located between your buttocks. If it is sore, it makes sitting very difficult.

Discs
The discs act as shock absorbers for the spine and allow for movement between the vertebrae. There are discs between each vertebra in the spine. The disc is like a jelly donut. It has a tough outer layer (annulus) and a jelly-like center (nucleus).

As we grow older, the discs dry out a little. It is the center portion of the disc that can squirt out (rupture, herniate, slip) and put pressure on the nerves. For more information on discs, please read "Understanding Spinal Discs."

Discs are labeled by the vertebrae they are located between. For example, L4-L5 would be the disc between the fourth and fifth vertebrae in the lumbar spine (low back).

Disc/Bone Column
Vertebrae are stacked on each other to form the spinal column. Between the vertebrae are the discs. Behind the disc bone column is the nerve channel or spinal canal through which the nerves travel from your brain to your arms and legs.

There are other portions of the vertebrae that make a protective cover for the spinal cord and nerves.

Spinous Process
The vertebrae have some prominent parts, for example, the spinous process. The spinous process is the part of the vertebra that you feel by pressing on your back.

Transverse Process
The transverse process comes off each side and looks like a wing. There are many muscles that attach to the transverse process to help with bending, twisting and just standing still.

Facet Joints
Between these two vertebrae are small joints called "facet joints" that allow you to move. Sometimes these joints can get sore and cause problems. For more information, please read "Facet Joint Syndrome".

Nerve Column
Behind the bone column is the nerve column. Part of each vertebra surrounds the spinal cord and nerve column.

At each level (vertebra) there is a nerve that leaves the nerve column on each side. These nerves go to the arms and fingers in the cervical spine (neck). In the lumbar spine (low back) these nerves go to the legs and feet.

It is this close relationship between the disc/bone column and the nerve column that explains why spine problems can cause symptoms (e.g., pain or numbness) in your arms and legs.