Jelly Donuts and Your Back

I have found that many people, myself included, are confused about the terms associated with disc problems in the spine.  I could go to my anatomy and physiology textbook or a scholarly journal to describe how the spine, vertebrae, and intervertebral discs work, but as interesting that would be for me, it is unlikely to add clarification on the subject.  Instead let me demonstrate the difference between slipped, bulging and herniated disc through a series of drawings by yours truly.

Here you have a lovely example of two vertebrae in the lower back.  The round flat parts that look like stumps are called the vertebral body.  On the right side in this drawing is the vertebral foramen, which is a fancy name for opening.  This is where the spinal cord passes through as indicated by the tube at the top of the drawing.  As the spinal cord passes through spinal nerves branch off through openings in order to communicate with different areas of the body.  So even though I am having pain in my butt and numbness in my calf, ankle, and foot, the source of the problem is the compressed nerve root in the spine.  In between the two vertebral bodies is the lovely yet elusive intervertebral disc illustrated below as a jelly donut:

It should be noted that is far easier to draw a complex lumbar vertebra than it is to draw a jelly donut.  So the intervertebral disc is like a jelly donut.  The dough is the tougher outer layer (anulus fibrosis) that contains the jelly which is the softer squishier inner layer (nucleus pulposus).

If you were to take two drinking glasses and invert them,with the jelly donut inbetween them, you would have the basic structure of the vertebrae and intervertebral disc.  Like so:

That jelly donut separates the glasses and keeps the fragile glass from clashing, scratching, and breaking.

If you were to exert gentle pressure on the glasses the jelly donut would squish out beyond the edges of the glasses.  If you were to press on the right the jelly donut would compress on the right and compensate by bulging on the left, hence the term bulging disc.  This is not abnormal and is the function of the intervertebral discs.  They allow the flexibility in the spine that allows us to bend, twist and turn.  However when the disc extends into the opening the spinal cord passes through it can irritate surrounding tissues and cause pain and discomfort.  This is called a slipped or bulging disc.  No worries though, the disc is solidly in place and can't actually slip out of place.

If you were to exert a large amount of pressure, say in a fall, the soft inner jelly squirts out.  It might be better to view the jelly as warm mozzarella cheese, but who has ever heard of a mozzarella donut?  Warm cheese would ooze and goo, but would still remain stringy and connected to the inside of the donut.  When the jelly/cheese/nucleus pulposus "squirts" out you have a herniated disc.  The herniation may compress the nerve root rather than just irritating it and you get a lack of communication between the nerve and the muscles etc they innervate, causing twitching, tingling, numbness, loss of reflexes, and movement of those muscles and tissues.

Sometimes the body takes notice of a large herniation and works harder to fix it than a small herniation.   I guess it is kind of like getting a splinter vs a tree branch stuck in your skin.  The tree branch is much more noticeable so we yank it out, whereas a splinter might not be noticed and may fester.  

So there you have it.  I better you never knew there was a connection between your spine and jelly donuts!