Which of the following best describes reversible cell injury?

• A. Membrane blebbing
• B. Nuclear fragmentation
• C. Cell swelling
• D. Membrane rupture

Answer: (C)

Reversible cell injury is marked by cellular swelling from failure of ATP-dependent ion pumps. When the Na+/K+ ATPase is impaired, sodium accumulates inside the cell and water follows, causing the cell and its organelles to swell. The plasma membrane stays intact, so the cell can recover if the stress is removed. Blebbing of the membrane can occur in this phase, but the hallmark feature is swelling. If the injury persists, the cell loses membrane integrity and undergoes irreversible changes, such as membrane rupture and nuclear fragmentation, leading to cell death.