Spine Anatomy 101
I never much cared for anatomy class. Dead bodies, the cold, and the smell were just not the way I liked to spend an afternoon. Every first year medical student spends hours in the anatomy room because learning the parts is important, but even more important is knowing what those parts do and how they work–functional anatomy. Thankfully, studying functional anatomy requires warm, live people who don’t usually smell. Let’s learn some parts without the smell because if you understand the parts, then you will understand the treatment.
Getting down to the framework of your body is the skeleton which holds you upright, otherwise you would be a blob of gooey mush. As part of the skeleton, the spine is your backbone that bridges the span between your head and your butt. Because it is a bridge, the spine has passive, stationary structures (bones, ligaments, and discs) which don’t “do” anything except provide support for the whole body. However, these parts of the spine would be worthless without the active muscles which make them strong and make them move. Last, but not least, is the control system (the nerves) which send instructions from the brain to the spine and the rest of the body. The passive, active, and control parts are the basic building blocks of your spine.
Speaking of blocks, the spine is like a bunch of blocks stacked on top of each other (see image). These blocks have a fancy medical name–vertebrae. These 33 vertebrae form a tube that shelters your spinal cord (the huge superhighway of nerves that connects to the brain). In between each body of the vertebrae is the squishy disc. I like to think of the discs like little balloons which act like shock absorbers. These discs are not the only way the spine bones connect to each other. Like two legs on a stool, the facet joints (see image) at every level join vertebrae together and further stabilize this tall stack of bones. Holding everything tightly bound are the rubber bands–the ligaments. All of these passive parts put together form the spine that like a bridge has strategic curves that can hold up some of the biggest loads. (Every bridge has a breaking point, but we will talk about that in later articles.) Please notice that the spine is broken down into sections: the cervical spine (the neck), the thoracic spine (the mid-back), the lumbar spine (the low back), and the tailbone (see image). Because the spine is not a stiff stick, let’s talk about the muscles that make it move and bend.
If it was not for the muscles, your backbone could only carry 5 pounds. Since I have never seen a five pound adult before, we need to talk about these active parts–the muscles. Go ahead, look at your biceps (Popeye or Olive Oil?). The biceps are big muscles, but there are bigger ones that cover the entire length of the spine. Better yet, go to your local butcher and ask to see the back straps. Then you will know what I mean by big. These huge, global muscles create large movements like bending. But, these muscles are not very good at supporting the spine. So, small, local muscles which lie close to the bones, discs, and ligaments help to stabilize the backbone. Both the global muscles and local muscles are actively supporting you right now.
What if you want to move? Instructions for movement are sent through the nerves which are the information superhighway of your body. How does that work? Visualize this: your butt is getting sore from sitting…BAM! Your brain just created a signal which flashed down the spinal cord to the back, butt, and leg muscles… They are told to “Move it!” With a slight shift, your butt is feeling better. Without the nerves, none of the movement is possible. Humans really are “just a bundle of nerves” and those nerves control everything.
Now you know about the parts in the spine that have either one of these basic jobs: passive support, active movement, or control messenger. Best of all, you did not have to spend hours in a smelly, cold anatomy lab. Yuck! The spine is critical for providing support for your entire body: your head, your legs, your arms, and your guts. So, you’d better take care of your backbone and knowing these parts will help you navigate on the road to spine health.
Christina Lasich, M.D., wrote about chronic pain and osteoarthritis for HealthCentral. She is physiatrist in Grass Valley, California. She specializes in pain management and spine rehabilitation.