Cortical bone is a dense and rigid layer of calcium-rich osseous tissue that makes up the outer layer of a bone, explains InnerBody. This compact bone layer is cylindrical in shape with a honeycombed structure, providing thousands of tiny canal-like passageways for nerves and blood vessels.
Arizona State University School of Life Sciences explains that bones are comprised of three layers: compact or cortical bone, spongy bone and bone marrow. Cortical bone tissue is very strong as it supports the weight of the body and is composed of parallel osteon units, which are comparable to a bundle of straws. Each osteon is composed of a central canal containing nerves and blood vessels, with osteocyte cells encircling the canal like the rings of a tree. Roughly 80 percent of the bone in the human body is composed of cortical bone tissue.