Light micrograph of a cross-section of normal human compact bone tissue, as found in the shafts of the long bones such as the femur. The rings correspond to concentric bands of calcified material called lamellae. They are centered around a Haversian canal (white circle) a channel for the nerves and blood & lymph vessels which run the entire length of the bone. The spider-like areas surrounding the canal are lacunae, holes in the bone occupied by osteocytes or bone cells. The active form of the osteocyte is the osteoblast cell, responsible for bone formation. Each canal and its surrounding lamellae form an Haversian system. Magnification: unknown.