Final answer:
Secondary ossification centers contribute to bone development following the appearance of a primary ossification center, with fusion occurring in a timeline reflective of skeletal maturity. For example, in the femur, fusion sequences follow the sequence of lesser and greater trochanters, followed by femoral head and distal condyles. The dens' secondary ossification center starts forming around age 3 and fuses between ages 12 to adulthood.
Step-by-step explanation:
The process of bone formation from sectional growth is known as endochondral ossification. For instance, in the femur's developmental process, a primary ossification center appears first, followed by multiple secondary ossification centers. These secondary centers contribute to the formation of the bone ends, which are separated by epiphyseal plates that permit further elongation.
Each secondary ossification center is fused following a specific timeline, reflecting the person's progression towards skeletal maturity. For example, in the femur, the lesser trochanter fuses around puberty, the greater trochanter a year later, and the distal condyles during late adolescence. This order of fusion ensures the continuous development and eventual unification of the bone structure.
In the context of the dens, or odontoid process of the axis (the second cervical vertebra), a secondary ossification center starts to form at the tip of the dens around age 3 and will typically fuse between 12 and adulthood. This knowledge is critical when analyzing bone development and maturity in radiographic exams, as unfused epiphyseal plates might be confused with fractures given their relative radiolucency.