What is the correct sequence of steps in bone repair? 1. Cartilage in the external callus is replaced by bone. 2. A hematoma occurs. 3. An internal callus forms at the site of injury. 4. Osteoclasts and osteoblasts remodel the bone at the site of repair. 4, 2, 3, 1 O2, 3, 1, 4 2, 1, 3, 4 3, 1, 4, 2 1, 2, 3, 4
The Correct Answer and Explanation is :
The correct sequence of steps in bone repair is:
2, 3, 1, 4
Here’s the explanation for each step:
- Hematoma formation (Step 2): When a bone fractures, blood vessels in the bone and surrounding tissues are ruptured, causing bleeding. This results in the formation of a hematoma (a clot) at the fracture site. The hematoma is an important first step because it stabilizes the fracture and initiates the inflammatory response that promotes healing.
- Formation of the internal callus (Step 3): After the hematoma forms, the body begins to lay down a framework of collagen and cartilage, creating the internal callus within the fracture site. This soft callus serves as a bridge between the fractured bone ends, helping to stabilize the fracture during the healing process.
- Cartilage is replaced by bone (Step 1): Over time, the cartilage in the external callus (the callus that forms outside the fracture site) is gradually replaced by bone tissue through a process called ossification. This step turns the initially soft callus into a bony structure, which strengthens the bone and provides better support to the fracture site.
- Bone remodeling (Step 4): Once the fracture has been stabilized and a bony callus has formed, osteoclasts (bone-resorbing cells) and osteoblasts (bone-forming cells) work to reshape and remodel the bone. This remodeling phase restores the bone to its original shape and strength. It may take months or even years for the bone to fully remodel to match the surrounding bone.
In summary, the healing of bone occurs in an orderly sequence: first a hematoma forms (Step 2), followed by the formation of an internal callus (Step 3). Cartilage in the external callus is then replaced by bone (Step 1), and finally, bone remodeling occurs (Step 4) to restore the bone to its original form and function.