The concentric circles of bone laid down around bone-forming cells are known as lamellae, which are part of the structure of compact bone. These circles are formed by osteoblasts, the cells responsible for bone formation. When osteoblasts secrete osteoid, which is the organic component of the bone matrix, they become trapped in the matrix they create. As they are trapped, they differentiate into osteocytes, which are the mature bone cells that maintain the bone matrix.
Each layer or lamella is oriented in a particular direction, and the alternating orientations of these lamellae provide strength to the bone while allowing it to remain lightweight. This layered structure is critical for the mechanical properties of bone, making it both strong and resilient against various forces and types of stress. The central canal of each osteon, surrounded by these concentric lamellae, contains blood vessels and nerves, playing a vital role in the nourishment and communication within the bone tissue.