I've heard the inside of a spinal disc is made of a jelly kind of substance. What's really in it?

Discs located between the vertebral bones of the spine have two parts. The inside called the nucleus is a gel-like cushion. The outer shell called the annulus is more tough and fibrous.

Scientists report the content of the nucleus as water, collagen, and proteoglycan. Collagen is a member of the protein family. It's what gives connective tissue its strength and flexibility. Interestingly, collagen turns into a gel like the nucleus when it's boiled.

So far, 20 different types of protein have been identified. Proteoglycan is another member of the protein family. It has a large amount of water, but we aren't sure what it does exactly. It's found on the surfaces of every cell in our body.

Researchers hope to find out what happens when the disc ages or is injured. Through this knowledge, we may be able to find ways to prevent disc degeneration over time.