Q.Write about the mechanism and healing of bone fracture.

Step 1. Formation of haematoma. When a bone breaks, torn blood vessels cause haemorrhage; the pooled, clotted blood forms a haematoma at the fracture site, and the surrounding tissue becomes swollen, painful and inflamed, with some bone cells dying from loss of nutrition.

Step 2. Formation of fibrocartilaginous callus. Within a few days, capillaries grow into the haematoma and phagocytic cells clear debris, while fibroblasts and osteoblasts migrate in from the periosteum and endosteum; fibroblasts lay down fibres and chondroblasts secrete cartilage matrix, which calcifies into a soft fibrocartilaginous callus.

Step 3. Formation of bony callus. New spongy-bone trabeculae appear within the fibrocartilaginous callus, gradually converting it into a harder bony callus, with firm union forming over roughly two months to a year. …

Walk through the four healing stages in order, describing the cell types a …

• Skipping the intermediate soft (fibrocartilaginous) callus stage and jumping straight from clot to hard bone, …