MICROANATOMY

Detailed explanation-1: -The increase in diameter is called appositional growth. Osteoblasts in the periosteum form compact bone around the external bone surface. At the same time, osteoclasts in the endosteum break down bone on the internal bone surface, around the medullary cavity.

Detailed explanation-2: -Long bones lengthen at the epiphyseal plate with the addition of bone tissue and increase in width by a process called appositional growth.

Detailed explanation-3: -The periosteum is a complex structure composed of an outer fibrous layer that lends structural integrity and an inner cambium layer that possesses osteogenic potential. During growth and development it contributes to bone elongation and modeling, and when the bone is injured, participates in its recovery.

Detailed explanation-4: -While bone is replacing cartilage in the diaphysis, cartilage continues to proliferate at the ends of the bone, increasing bone length. These proliferative areas become the epiphyseal plates (physeal plates/growth plates), which provide longitudinal growth of bones after birth and into early adulthood.

Detailed explanation-5: -The epiphyseal plate is responsible for longitudinal bone growth. The proliferative zone is the next layer toward the diaphysis and contains stacks of slightly larger chondrocytes. It makes new chondrocytes (via mitosis) to replace those that die at the diaphyseal end of the plate.