A bone cell, formed when an osteoblast becomes embedded in the matrix it has secreted.

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

Answer: (B)

The concept here is how bone cells mature once they become surrounded by the bone matrix they secreted. Osteoblasts lay down the new bone matrix (osteoid) and promote mineralization. When some of these osteoblasts become completely embedded in that matrix, they stop lining the surface and differentiate into mature bone cells called osteocytes. These osteocytes sit in tiny spaces called lacunae and extend processes through small channels called canaliculi to communicate and coordinate with other bone cells, helping maintain bone tissue and sense mechanical load. The other two cell types—cartilage cells and bone-resorbing cells—are different: chondrocytes are cartilage cells, and osteoclasts break down bone.