Final answer:
Appositional growth involves the addition of new bony tissue by osteoblasts at the bone surface and the breakdown of bone by osteoclasts on the inner surface, facilitating the thickening of bones without increasing their weight.
Step-by-step explanation:
Appositional Growth of Cartilage
Appositional growth refers to the process by which cartilage increases in size by adding new layers of cells and extracellular matrix to those that already exist. It mainly occurs at the surface of the tissue, allowing for the thickening of long bones. In relation to long bones, this growth is a component of overall bone growth and development, with a focus on increasing bone diameter rather than length, the latter of which is achieved by interstitial growth at the epiphyseal plate.
During appositional growth, osteoblasts, which are cells that synthesize bone, add new bone tissue to the surface. These cells, which originate from osteoprogenitor cells, lay down new matrix and eventually become enclosed within it, differentiating into osteocytes. Concurrently, osteoclasts, another type of bone cell, resorb bone tissue from the inner surfaces, maintaining a balance that allows bones to thicken and strengthen without becoming overly dense and heavy.
In addition to its role in bone development and growth, appositional growth is also involved in the process of bone remodeling and repair. In situations such as bone repair, osteoblast activity is pronounced as these cells fill in gaps or breaks with new bone tissue, reflecting the dynamic nature of bone — constantly being broken down by osteoclasts and rebuilt by osteoblasts.
Appositional growth enables the thickening of bones through activity by osteoblasts and osteoclasts. It contributes to bone growth, remodeling, and repair by adding and resorbing bony tissue respectively.