Which bone cell type is primarily responsible for bone resorption?

Which bone cell type is primarily responsible for bone resorption?

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

Answer: (A)

Bone resorption is carried out by osteoclasts, specialized, multinucleated cells that attach to the bone surface and create a sealed resorption compartment. They secrete acids to dissolve the mineral component and proteolytic enzymes like cathepsin K to break down the organic matrix, actively carving out small pits in the bone. Their activity is tightly regulated by signals from osteoblast-lineage cells, notably the RANKL-RANK-OPG system, which modulates their formation and activity. Osteoblasts, in contrast, are responsible for laying down new bone matrix and promoting mineralization. Osteocytes are former osteoblasts embedded in the bone that help sense mechanical load and coordinate remodeling but do not resorb bone themselves. Chondrocytes live in cartilage, not bone, and thus do not resorb bone. Therefore, the cell type primarily responsible for bone resorption is osteoclasts.

Bone resorption is carried out by osteoclasts, specialized, multinucleated cells that attach to the bone surface and create a sealed resorption compartment. They secrete acids to dissolve the mineral component and proteolytic enzymes like cathepsin K to break down the organic matrix, actively carving out small pits in the bone. Their activity is tightly regulated by signals from osteoblast-lineage cells, notably the RANKL-RANK-OPG system, which modulates their formation and activity. Osteoblasts, in contrast, are responsible for laying down new bone matrix and promoting mineralization. Osteocytes are former osteoblasts embedded in the bone that help sense mechanical load and coordinate remodeling but do not resorb bone themselves. Chondrocytes live in cartilage, not bone, and thus do not resorb bone. Therefore, the cell type primarily responsible for bone resorption is osteoclasts.