One of the three layers of a bone, compact bone tissue is the rigid, dense outer layer of bone that consists primarily of calcium and minerals. Also called cortical bone, compact bones are so hard that a saw is needed to cut through it for surgery.
Compact bone is cylindrical in shape and filled with thousands of openings in which blood vessels and nerves carry oxygen and nutrients to the bone. Compact bone is so dense that it does not register pain. If a bone breaks, damaged nerve fibers send pain signals through the compact bone to the brain. The center of compact bone contains the medullary cavity, which protects spongy bone marrow.