Endochondral ossification is a process where bone tissue is formed from a cartilage model. This process primarily occurs during the development of long bones, such as those in the arms and legs. Initially, a cartilage template is created, which is gradually replaced by bone as the body grows. During endochondral ossification, chondrocytes (cartilage cells) enlarge and die, creating spaces that are filled with blood vessels and osteoblasts (bone-forming cells). These osteoblasts then produce bone matrix, leading to the hardening of the structure. This process is crucial for the proper growth and development of the skeletal system.