In diagrams of a long bone growth plate, which zone shows active cell proliferation?

In diagrams of a long bone growth plate, which zone shows active cell proliferation?

• A. Hypertrophy
• B. Proliferation
• C. Resting zone
• D. Ossification

Answer: (B)

Active cell proliferation is seen in the zone where chondrocytes are rapidly dividing and forming columns. Here, cells mitotically divide and add new cartilage matrix, pushing older cells toward the next zone and lengthening the bone. This contrasts with the resting zone, which mainly holds quieter chondrocytes; the hypertrophic zone where cells grow larger rather than divide; and the ossification area where cartilage is replaced by bone. So the proliferative zone is the region responsible for the active production and division of cartilage cells that drives growth in length.

Active cell proliferation is seen in the zone where chondrocytes are rapidly dividing and forming columns. Here, cells mitotically divide and add new cartilage matrix, pushing older cells toward the next zone and lengthening the bone. This contrasts with the resting zone, which mainly holds quieter chondrocytes; the hypertrophic zone where cells grow larger rather than divide; and the ossification area where cartilage is replaced by bone. So the proliferative zone is the region responsible for the active production and division of cartilage cells that drives growth in length.