Final answer:
The metaphyses of a 40-year-old's long bones experience appositional growth, which is the thickening of bones in diameter through the ongoing remodeling process involving osteoblasts and osteoclasts even after longitudinal growth has ceased.
Step-by-step explanation:
The metaphyses of a 40-year-old's long bones have undergone a specific type of bone growth known as appositional growth. This is not to be confused with longitudinal growth, which occurs via the epiphyseal plate and usually ceases after adolescence. After this point, the epiphyseal plates close and are replaced by epiphyseal lines, indicating that the bones have reached their maximum length. However, bones can continue to thicken in diameter through the activity of osteoblasts and osteoclasts, which work in unison to remodel the bone and maintain its overall integrity and strength as part of the bone remodeling process.
Growth in diameter, or appositional growth, involves osteoblasts adding new bone tissue beneath the periosteum, while osteoclasts resorb old bone lining the medullary cavity. This action allows the bone to increase in size without becoming too heavy, which is important for maintaining the proper balance of form and function in the skeletal system.