(named for the English anatomist C. Havers, 1650-1702), tubular cavities in the compact matter of lamellar bone in higher vertebrates and humans. In hollow bones the Haversian canals run parallel to the longitudinal axis, in flat ones parallel to the surface, and in the bodies of the vertebrae perpendicular to the axis. Each Haversian canal is surrounded by concentrically placed bony plates (lamellae); together they form a structural unit of the bone, the Haversian system. Between lamellae in the cavities there are bone cells—osteocytes.

Inside the Haversian canals are blood vessels, nerves, and mesenchymal cells, which, in the rebuilding of bone, form osteoclasts, which resolve bone, and osteoblasts, which manufacture it. Small canals thread through the osteal lamellae and open into the Haversian canals, uniting the osteal cavities. Haversian canals of neighboring systems for some distance may unite into stable supporting structures.