Question

question 44

correctly order the following key steps in the process of endochondral ossification.

1. chondrocytes die.
2. osteoblasts build the bone collar on the external surface of the bone.
3. perichondrium is invaded by blood vessels.
4. in the primary ossification center, osteoblasts replace calcified cartilage with early spongy bone.
5. perichondrial cells differentiate into osteogenic cells then into osteoblasts.

3, 1, 4, 5, 2
3, 5, 2, 1, 4
4, 3, 2, 1, 5
3, 1, 2, 3, 5

Explanation:

Analyze the initial steps of ossification

Using the Endochondral Ossification knowledge point

The process begins when blood vessels invade the perichondrium surrounding the hyaline cartilage model (Step 3). This influx of nutrients triggers the next event.

Trace cellular differentiation and collar formation

Using the Endochondral Ossification and Bone Cells knowledge points

Following vascularization, perichondrial cells differentiate into osteogenic cells and then into osteoblasts (Step 5). These newly formed osteoblasts then build a bone collar on the external surface of the cartilage model (Step 2).

Determine cartilage calcification and chondrocyte death

Using the Endochondral Ossification knowledge point

The bone collar cuts off diffusion to the internal cartilage. Consequently, internal chondrocytes hypertrophy, the surrounding matrix calcifies, and the chondrocytes die (Step 1).

Identify primary ossification center development

Using the Endochondral Ossification knowledge point

Finally, a periosteal bud invades the internal cavity. In this primary ossification center, osteoblasts replace the calcified cartilage matrix with early spongy bone (Step 4). This yields the sequence: 3, 5, 2, 1, 4.

Answer:

• 3, 1, 4, 5, 2
• 3, 5, 2, 1, 4 (Correct answer)
• 4, 3, 2, 1, 5
• 3, 1, 2, 3, 5