What is the Nucleus Pulposus?

Intervertebral Disc
Intervertebral Disc. BSIP/UIG/Collection:Universal Images Group/Getty Images

Nucleus Pulposus

The nucleus pulposus is the soft center of the intervertebral disc. It is contained by a strong covering (which is made of 3 concentric layers of tough fibrous tissues). The covering around the nucleus pulposus is known as the annulus fibrosus.

Nucleus Pulposus as Shock Absorber

The nucleus pulposus is responsible for shock absorption for the spine.

You might think of it as a pillow or cushion that lives in between two vertebrae and that moves as you move.

The quality of the movement the nucleus pulposus makes is similar to swiveling. In this way, the nucleus pulposus accommodates the various (and numerous) spinal motions you make during the day. And because of its water balloon like shape and consistency, it is involved in many types of movements  - from shifting your position while you sit, to working out and playing sports, to unloading groceries and putting the in the fridge and much more.

Let's take the example of bending forward to pick something up from the floor. This action may involve a motion called forward spinal flexion, which is basically rounding over at the spine. When you bend forward this way, the spinal bones come closer together in front, which pushes the movable nucleus toward the back.

As you can see, because it is responsive to your movements, the nucleus pulposus helps to prevent pressure on the spine as you sit, stand, walk or engage in activities.

 That said, bending forward at the spine (as opposed to bending at the hips, knees, and ankles) when you have to lift or pick things up is not recommended by spine experts as safe. This is because it increases your risk for a disc herniation.

Aging and the Nucleus Pulposus

In young people, the nucleus pulposus is made mostly of water (which makes the risk of a disc herniation higher in this age group).

As we get older, the disc, but especially the nucleus pulposus dries out. This dehydration results in a significant loss of disc height, so by the age of 60 to 70, the disc is composed entirely of fiber, and shock absorption for the spine is for the most part, lost.

If you're concerned about the health of your discs, check out the following articles for more specific information:

Also Known As: Nucleus

Common Misspellings: Nucleus Pulposis

Examples: A herniated nucleus pulposus can cause low back pain if it presses on a nearby nerve root.

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