How did vertebrea prevent from griding against one another?

Discs are made up of an outer fibrous shell within which is a gel-like filling - I see we're back to doughnuts again! More accurately called intervertebral discs because of their location in the body, these important structures don't only act as shock absorbers but also behave like a flexible glue since while holding adjacent vertebrae together - and preventing them from grinding against each other - they also allow some movement of the vertebrae.