Nucleus Pulposus and How It Helps Your Spine

The nucleus pulposus is located in the spine, between two vertebrae, where it plays a major role in providing the spine with shock absorption during movement. It prevents bone to bone contact, reducing the possibility of injuries and pain.

Illustration of the inside of the spine
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What Is the Nucleus Pulposus?

The nucleus pulposus is part of the intervertebral disc. It is the soft filling located in the center of the disc.

It is surrounded by a strong covering consisting of 3 concentric layers of tough fibrous tissue. The covering is called the annulus fibrosus.

Nucleus Pulposus as Shock Absorber

Each intervertebral disc is a shock-absorbing cushion that's located between adjacent spinal bones. The centralized nucleus pulposus is an essential component of the disc that helps provide it with its shock absorption properties.

The intervertebral disc moves as you move. For example, when you arch your back, the disc migrates forward a bit; when you twist, the disc twists, too.

The strong outer fibers of the annulus fibrosis package the nucleus pulposus and keep it safely inside.

Spinal Action

Your spinal movements are supported by your intervertebral disc. And it's the nucleus pulposus that allows the disc to be so moveable. When you bend, twist, arch or tilt your spine, the nucleus pulposus swivels, which allows it to accommodate these actions.

Many times per day, the repeated spinal actions of twisting, tilting, arching, rounding, etc. contribute to activities like shifting your position while you sit, working out and playing sports, unloading groceries and putting them 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 pulposus toward the back.

Disc Injury

With persistent or excessive spinal flexion, the disc may be pushed too far back.

If the fibers of the annulus fibrosus are weak or torn, the nucleus pulposus may escape between them. Generally, the nucleus pulposus will escape in a combination side and back direction, which approximately corresponds to the location of the very sensitive nerve root with which it may come into contact. When it does, it may come into contact with the nearby spinal nerve root, causing pain and other symptoms. This injury is called a herniated disc.

The two most common causes of a disc herniation are degenerative wear and tear changes of the disc and trauma to the disc. Disc degeneration occurs with age; it weakens the fibers of the annulus, allowing the nucleus pulposus to either distend or bulge, or to herniate.

Aging and the Nucleus Pulposus

Disc degeneration tends to come with age and it also can occur with injuries to the area.

In young people, the nucleus pulposus is made mostly of water. So for this age group, a herniation due to trauma is more likely than in older people.

But as we get older, the disc, especially the nucleus pulposus dries out. This dehydration leads to a significant loss of disc height. By the time you're 60 or 70, your discs may be composed entirely of fiber. In this case, the shock absorption function of the disc is, for the most part, lost.

A Word From Verywell

The near-liquid consistency of the nucleus fibrosis makes it responsive to movement. But another one of its functions is to buoy the spine; this helps prevent pressure on the bones.

A good rule of thumb when protecting your discs from injury on a day to day basis is to do your best to avoid forward spinal bending. Many times, you can replace that particular movement by bending at your hips, knees, and ankles.

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