Bone remodeling period

In bone physiology, the bone remodeling period describes the temporal duration (i.e. lifespan) of the basic multicellular unit (BMU) that is responsible for bone turnover. Historically, this was referred to as the sigma (σ) or sigma period, but the terminology is now outdated.For the remodeling to occur, appropriate cell signaling occurs to trigger osteoclasts to resorb the surface of the bone, followed by deposition of bone by osteoblasts. Together, the cells in any given particular region of the bone surface that are responsible for bone remodeling are known as the basic multicellular unit (BMU), and it is the average lifespan of the BMU that is referred to as the remodeling period. The size of a BMU is roughly 200μm in diameter, defined by the 100μm diffusion capability in bone. In bone physiology, the bone remodeling period describes the temporal duration (i.e. lifespan) of the basic multicellular unit (BMU) that is responsible for bone turnover. Historically, this was referred to as the sigma (σ) or sigma period, but the terminology is now outdated. Although bone may appear superficially as a static tissue, it is actually very dynamic, undergoing constant remodeling throughout the life of the vertebrate organism. This occurs with the synchronized action of osteoclasts and osteoblasts, cells that resorb and deposit bone, respectively. The remodeling period consists of the combined duration of the resorption, the osteoclastic reversal (the phase marked by shifting of resorption processes into formative processes) and the formation periods of bone growth and development. This period refers to the average total duration of a single cycle of bone remodeling at any point on a bone surface.