When most people mention their back, what they are actually referring to is their spine. The spine runs from the base of your skull down the length of your back, going all the way down to your pelvis. It is composed of 33 spool-shaped bones called vertebrae, each about an inch thick and stacked one upon another.
Each vertebra consists of the following parts:
The body is the largest part of the vertebrae and the part that bears the most weight.
The lamina is the lining of the hole (spinal canal) through which the spinal cord runs.
The spinous process is the bony protrusions you feel when you run your hand down your back.
The transverse processes are the pairs of protrusions on either side the vertebrae to which the back muscles attach.
The facets are two pairs of protrusions where the vertebrae connect to one another, including: