Lengthwise bone growth during infancy and youth occurs exclusively through which process?

Lengthwise bone growth during infancy and youth occurs exclusively through which process?

• A. Calcification of the matrix of the zone underlying articular cartilage
• B. Differentiation of osteoblasts into osteocytes
• C. Interstitial growth of epiphyseal plates
• D. The secretion of bony matrix into the medullary cavity

Answer: (C)

Lengthwise bone growth happens through interstitial growth of the epiphyseal plates. In infancy and youth, chondrocytes within the growth plate multiply and enlarge, lengthening the cartilage model. This cartilage is then progressively replaced by bone on the diaphyseal side (endochondral ossification), which pushes the ends of the bone farther apart and increases length. This process continues until the growth plate closes after puberty, ending length growth. The other listed processes are related to bone formation or remodeling but do not drive growth in length: calcification of matrix under articular cartilage is a different calcification event, differentiation of osteoblasts into osteocytes is a general step in bone formation without adding length, and secreting bone matrix into the medullary cavity pertains to cavity formation/remodeling rather than lengthening.

Lengthwise bone growth happens through interstitial growth of the epiphyseal plates. In infancy and youth, chondrocytes within the growth plate multiply and enlarge, lengthening the cartilage model. This cartilage is then progressively replaced by bone on the diaphyseal side (endochondral ossification), which pushes the ends of the bone farther apart and increases length. This process continues until the growth plate closes after puberty, ending length growth. The other listed processes are related to bone formation or remodeling but do not drive growth in length: calcification of matrix under articular cartilage is a different calcification event, differentiation of osteoblasts into osteocytes is a general step in bone formation without adding length, and secreting bone matrix into the medullary cavity pertains to cavity formation/remodeling rather than lengthening.