Which cell is primarily responsible for bone resorption during remodeling?

Which cell is primarily responsible for bone resorption during remodeling?

• A. Osteoblast
• B. Osteocyte
• C. Osteoclast
• D. Chondrocyte

Answer: (C)

Bone remodeling relies on a coordinated sequence where old bone is removed and new bone is formed. The cell that does the actual resorption is the osteoclast. These large, multinucleated cells come from the monocyte/macrophage lineage and attach to the bone surface to create a sealed resorption area. They pump acids and enzymes into this space—acid dissolves the mineral component, and enzymes like cathepsin K break down the organic matrix—creating a hollow pit that will later be filled by new bone laid down by osteoblasts. Osteocytes, the former osteoblasts embedded in bone, mainly sense mechanical signals and regulate remodeling; chondrocytes are cartilage cells, not the drivers of bone resorption in remodeling. So the osteoclast is the primary resorbing cell.

Bone remodeling relies on a coordinated sequence where old bone is removed and new bone is formed. The cell that does the actual resorption is the osteoclast. These large, multinucleated cells come from the monocyte/macrophage lineage and attach to the bone surface to create a sealed resorption area. They pump acids and enzymes into this space—acid dissolves the mineral component, and enzymes like cathepsin K break down the organic matrix—creating a hollow pit that will later be filled by new bone laid down by osteoblasts. Osteocytes, the former osteoblasts embedded in bone, mainly sense mechanical signals and regulate remodeling; chondrocytes are cartilage cells, not the drivers of bone resorption in remodeling. So the osteoclast is the primary resorbing cell.