Compact bone. Polarized light micrograph (PLM) of a section through human compact bone. Found in the walls of bones, this tissue forms concentric layers (lamellae, white) around Haversian canals (black circles), which contain blood, lymph vessels and nerves. The lamellae and canals together form a Haversian system. Many Haversian systems are arranged in columns running parallel to the long axis of the bone. Osteocytes, the cells responsible for the maintenance of the bony matrix, are housed in spaces known as lacunae (small black ovals). They link by projections of their cytoplasm held in tiny channels (canaliculi). Magnification: x50 at 6x7cm size x25 at 35mm size.