Compact bone, light micrograph. Compact bone, which forms a bone's outer layer, consists of concentric layers of collagen-containing matrix (lamellae, light brown), around Haversian canals, which contain blood and lymph vessels, and nerves. These canals run the length of the bone. The lamellae and canals together form a Haversian system, or osteon. Many systems are arranged in columns running parallel to the long axis of the bone. Osteocytes, the cells that maintain the bony matrix, are housed in small spaces known as lacunae (small dark dots). Magnification: x100 when printed at 15cm wide.