Compact bone. Polarized light micrograph (PLM) of a section through human compact bone. This type of bone comprises the dense walls of the shafts of long bones. Compact bone is arranged into concentric bony layers (lamellae) arranged around channels (Haversian canals one at center left, light blue) containing blood, lymph vessels and nerves. The lamellae and canals form a Haversian system. The Haversian systems are arranged in columns which run parallel to the long axis of the bone. The small dark spots are spaces (lacunae) which house osteocytes the cells responsible for the maintenance of the bony matrix. Magnification: x80 at 5x7cm , x100 at 6x9cm size.