Compact bone. Light micrograph of a section through human compact bone. This tissue forms concentric layers (lamellae, green) around Haversian canals (blue circles). The canals contain blood, lymph vessels and nerves. The lamellae and canals together form a Haversian system. Many systems are arranged in columns running parallel to the long axis of the bone. Osteocytes (small red ovals), the cells which maintain the bony matrix, are housed in spaces known as lacunae. Projections of their cytoplasm are held in channels called canaliculi (thin yellow lines). Dark field illumination. Magnification: x45 at 35mm size.