Which cell type is primarily responsible for bone resorption during remodeling?

• A. Osteoblasts
• B. Chondrocytes
• C. Osteocytes
• D. Osteoclasts

Answer: (D)

Bone remodeling involves removing old bone and replacing it with new bone. The cell type responsible for bone resorption is osteoclasts. These large, multinucleated cells attach to the bone surface and create a sealed resorption zone, where they secrete acid to dissolve mineral and proteolytic enzymes to break down the organic matrix. This activity forms resorption pits called Howship's lacunae. After resorption, osteoblasts come in to lay down new bone matrix and mineralize it. Chondrocytes are cartilage cells involved in cartilage formation rather than bone resorption, and osteocytes are mature bone cells that sense mechanical signals and help regulate remodeling but do not perform the resorption itself.