Compact bone. Light micrograph of a section through compact bone in the shaft of a long bone. Compact bone is a dense form of bone in which the bone units (lamellae) are tightly organised. Some, known as circumferential lamellae, form layers on the outer and inner surfaces of the bone. However, most of the lamellae are arranged in circular units called osteons or Haversian systems, which have a central cavity containing blood vessels. The spaces between the osteons are filled with interstitial lamellae and Volkmann's canals connect adjacent osteons to one another. Magnification: x23 when printed 10cm wide.