Cortical bone, also known as compact bone is one of two main types of osseous tissues. Cortical bone is dense and forms the surface of bones, contributing 80% of the weight of a human skeleton. It is extremely hard, formed of multiple stacked layers with few gaps.
The other major type of bone is trabecular or cancellous bone; it is spongy and makes up the bulk of the interior of most bones, including the vertebrae. Its main function is to support the body, protect organs, provide levers for movement, and (shared with cancellous bone) store minerals.