Question: Step 1

Answer: Cartilage enlarges; Chondrocytes die

Question: Step 2

Answer: blood vessels grow into perichondrium; cells convert to osteoblasts; shaft becomes covered with superficial bone

Question: Step 3

Answer: more blood supply and osteoblasts; produces spongy bone; formation spreads on shaft

Question: Step 4

Answer: Osteoclasts create medullary cavity; appositional growth

Question: Step 5

Answer: epiphysis centers calcify; blood and osteoblasts move in; secondary ossification centers