Which cells break down bone through resorption?

Which cells break down bone through resorption?

• A. Osteoblasts
• B. Osteoclasts
• C. Cartilage
• D. Tendon

Answer: (B)

Bone resorption is carried out by osteoclasts, large multinucleated cells derived from the monocyte/macrophage lineage. They attach to the bone surface and create a sealed resorption lacuna, where they acidify the local environment using proton pumps and carbonic anhydrase II to dissolve the mineral component (hydroxyapatite). They also release proteolytic enzymes like cathepsin K to digest the organic matrix, mainly collagen. This resorptive activity is balanced by osteoblasts, which lay down new bone matrix and promote mineralization. Cartilage and tendon do not resorb bone in the adult skeleton—cartilage serves other roles in joints and development, while tendons connect muscle to bone. Thus, the cells that break down bone through resorption are osteoclasts.

Bone resorption is carried out by osteoclasts, large multinucleated cells derived from the monocyte/macrophage lineage. They attach to the bone surface and create a sealed resorption lacuna, where they acidify the local environment using proton pumps and carbonic anhydrase II to dissolve the mineral component (hydroxyapatite). They also release proteolytic enzymes like cathepsin K to digest the organic matrix, mainly collagen. This resorptive activity is balanced by osteoblasts, which lay down new bone matrix and promote mineralization. Cartilage and tendon do not resorb bone in the adult skeleton—cartilage serves other roles in joints and development, while tendons connect muscle to bone. Thus, the cells that break down bone through resorption are osteoclasts.