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Bone remodeling


The amount of bone mass present in the skeleton is the result of formation and resorption.

This one turnover is directly related to the bodily need to maintain a physiological concentration of ionized calcium in organic fluids and especially the need to maintain the structural integrity of the skeleton.
In the normal physiological process, bone resorption and formation are closely related in time, degree and space, so that bone formation is only activated after an area of ‚Äč‚Äčabsorption is established. Bone metabolism is influenced by several factors. hormonal, local, behavioral and environmental, as well as mechanical, electrical, chemical and magnetic forces. This mechanism is relatively fast in trabecular bone and slower in cortical bone.
The osteoclasts They are recruited to the surface (a process called activation) and reabsorb a quantity of mineral, creating a cavity - the Howship gap - in the trabecular bone. This phase lasts for about two weeks and is followed by a period of apparent inactivity at the resorption site. During this phase, osteoclasts disappear and are replaced by macrophages, whose function is not entirely elucidated, but which appears to be depositing a cementing substance.
Because this process occurs between bone removal and its subsequent replacement, it is called the reversal phase. By an unknown signal, osteoblasts - cells that synthesize the new matrix - adhere to the surface of the cavity. These cells synthesize collagen and other non-collagenous proteins, which are secreted into the cavity to form the osteoid, a non-mineralized matrix that will later form new bone. This phase of formation may take several months to set up. Under normal conditions, the amount of new bone synthesized at each remodeling site is exactly the same as that removed by osteoclasts.

Adults are estimated to remodel 10 to 30% of your bone mass each year. This "preventive maintenance" makes the skeleton average around eight years old

Fractures and osteoclasts

Simply put, we can say that a fracture is the break of a bone. When it occurs, the normal procedure is the reduction of this fracture, that is, the approximation of the stumps (fractured parts), and the immobilization until the formation of the bone callus and its complete calcification.

The osteoclasts They are also involved in fracture repair. After bone breakdown, intense periosteum proliferation occurs. This leads to the formation of a ring, the bone callus, which involves the broken pieces. At the same time, osteoclasts initiate the removal of dead bone cells and the formed clot as there is considerable bleeding in the fracture.

O periosteum provides new immature bone starter cells, which provisionally join the separate pieces. Over time, bone callus remodeling occurs and, gradually, the bone structure is redone with the participation of osteoclasts and osteoblasts, until the fracture is consolidated.