A thick band of bone forms around a broken as it heals In time the thickened disappears Explain how this extra can disappear over time?

During the healing process of a fractured bone, a thickened band of bone called callus forms around the fracture site. This callus serves as a temporary support structure to stabilize the bone fragments and promote bone regrowth. However, over time, the excess bone material within the callus is gradually remodeled and reabsorbed, resulting in the disappearance of the thickened bone. Here's how this extra bone disappears:

1. Bone Remodeling: Bone tissue undergoes constant remodeling throughout life. This process involves the breakdown of old bone tissue by osteoclasts (bone-resorbing cells) and the formation of new bone tissue by osteoblasts (bone-building cells). In the case of the thickened callus, the excess bone material is gradually broken down and reabsorbed by osteoclasts.

2. Osteonal Remodeling: Osteonal remodeling is a specific type of bone remodeling that occurs within Haversian systems - cylindrical structures that run lengthwise in the compact bone. During osteonal remodeling, old bone tissue within an Haversian system is resorbed by osteoclasts, creating a Haversian canal. Subsequently, osteoblasts lay down new bone tissue within the canal, concentrically filling it in. In the case of the callus, the thickened bone may undergo osteonal remodeling, contributing to the removal of excess bone.

3. Modeling: Modeling is another aspect of bone remodeling that involves the overall shaping and reshaping of the bone. As the fractured bone heals and regains its function, the callus is remodeled to match the original shape and strength of the bone. This involves both the removal of excess bone and the deposition of new bone where necessary.

4. Mechanical Stress: Mechanical stress plays a significant role in bone remodeling. When a bone is subjected to mechanical forces, such as weight-bearing and muscle contractions, it responds by adapting its structure. In the case of the healed bone, the application of mechanical stress through regular physical activity can promote the remodeling of the callus and the removal of excess bone.

Through these processes of bone remodeling, osteonal remodeling, modeling, and the influence of mechanical stress, the thickened bone around the fractured site gradually disappears over time, leaving behind a fully healed and structurally sound bone.