Question

How did vertebrae prevent from grinding against one another?

Answer 1

Inter-vertebral discs separate vertebrae from one another. They are cushion-like discs which absorb the shock the body experience during movement and prevent the vertebrae from grinding against one another.

Answer 2

The intervertebral discs, which are between vertebrae, are the parts that prevent the vertebrae from grinding against one another.

The intervertebrals discs act as a cushion; they absorb the stress and shockw that occur during movement, preventing such grinding.