Light micrograph of a section through human compact bone, showing Haversian canals (circular regions) and volkmann's canals. The concentric rings surrounding the Haversian canals are called lamellae. The canals run along the long skeletal bones, and contain blood vessels, lymphatic vessels, and nerves. The lamellae are made of compacted collagen fibers and minerals produced by bone-forming cells that are called osteoblasts. The osteoblasts become trapped in the bone matrix at sites called lacunae (small dark spots spaced throughout).