Growth in Length of Long Bones
Proliferation (Growth) Zone
cartilage on diaphysis side is rapidly dividing (new cells formed move up, pushing epiphysis away from diaphysis and causes lengthening) growing fast
Resting (Quiescent) Zone
cartilage on epiphyseal plate, inactive (top zone)
Ossification Zone
chondrocyte deterioration leaves long spicules of calcified cartilage at epiphysis-diaphysis junction (bone structure is complete) bottom zone
Spicules
eroded by osteoclasts and covered with new bone by osteoblasts forming spongy bone
Epiphyseal Plate
maintains constant thickness, closure of this allows growth of length to occur
Hypertrophic Zone
older chondrocytes closer to diaphysis (cartilage lacunae enlarges, increasing length, and erodes causing interconnecting spaces)
Calcification Zone
surrounding cartilage matrix calcifies (chondrocytes die and deteriorate) matrix hardens