Which of the following best describes the zone of cell hypertrophy in an epiphyseal plate?

• A. Chondrocytes undergo rapid mitosis to increase cell number.
• B. Osteoblasts deposit bone matrix on calcified cartilage.
• C. Chondrocytes enlarge and their lacunae expand, causing the matrix to thin.
• D. Chondrocytes die and the matrix begins to calcify.

Answer: (C)

Verified step by step guidance

1. Understand the context: The epiphyseal plate, also known as the growth plate, is a region of cartilage found in growing bones. It is responsible for longitudinal bone growth and consists of several zones, each with distinct cellular activities.
2. Identify the zone of cell hypertrophy: This zone is characterized by the enlargement of chondrocytes (cartilage cells). These cells increase in size rather than dividing, which is distinct from the rapid mitosis seen in the zone of proliferation.
3. Explain the process: In the zone of hypertrophy, the chondrocytes enlarge, and their lacunae (the spaces they occupy) expand. This enlargement causes the surrounding cartilage matrix to thin, preparing the area for subsequent calcification and ossification.
4. Clarify why other options are incorrect: For example, rapid mitosis occurs in the zone of proliferation, not hypertrophy. Osteoblast activity and matrix calcification occur later in the ossification process, beyond the hypertrophic zone.
5. Summarize the correct description: The zone of cell hypertrophy is best described as the region where chondrocytes enlarge, their lacunae expand, and the matrix thins, setting the stage for further bone development.