How are the diaphysis, metaphysis, and epiphysis arranged in a long bone?

In a long bone, the diaphysis, metaphysis, and epiphysis are arranged in a specific structural sequence that supports the bone's function and growth.1

• Diaphysis: This is the central, tubular shaft of the long bone. It is characterized by a thick cortex and a central medullary cavity.12
• Metaphysis: Located at the ends of the diaphysis, this region flares outward as the bone transitions from the tubular shaft toward the joint surfaces. It functions to transfer loads from the joints to the diaphysis.1
• Epiphysis: This is the terminal end of the long bone, which comprises the bony substructure of the joint surface. It consists primarily of cancellous bone.13

Prior to skeletal maturity, the epiphysis is separated from the metaphysis by a cartilaginous structure known as the growth plate (or physis), which is responsible for longitudinal bone growth. Once full growth is attained, the growth plate is replaced by bone, and the epiphysis becomes fixed to the rest of the bone.134