Bone structure at birth, bone development, cartilage structure, pediatrics. This illustration shows the anatomy of a humerus in frontal section. From birth to childhood, the bone structure is cartilaginous and flexible. The center of the bone presents a vascularized medullary cavity. Compact bone is formed around this cavity (beige area in the center). At each end of this area is the epiphyseal cartilage (in pink). This area is more important in infants than in children. It has disappeared in the adult. Then the ends of the bone (epiphyses) are very vascularized. It is at this level that the secondary ossification center is located. The bone can thus grow gradually with the child. A cut section is indicated at the level of the shaft of the bone. It is shown top view at the bottom of the illustration. This makes it possible to see the structure of the bone in horizontal section. The bone is covered with a membrane, the periosteum. Then a part of compact bone, and in the center the medullary cavity.