Which of the following morphological changes is characteristic of reversible cell injury?

Question

Accepted Answer

A. Cellular swelling with intact plasma membrane. ## Reversible vs Irreversible Cell Injury

**Key Point:** Reversible cell injury is characterized by changes that can be restored to normal if the injurious stimulus is removed before the point of no return is reached.

### Morphological Features of Reversible Injury

**High-Yield:** The hallmark of reversible injury is **cellular swelling (hydropic change)** with preservation of the plasma membrane integrity. This occurs due to:
- ATP depletion → failure of Na⁺/K⁺-ATPase pump
- Influx of Na⁺ and water into the cell
- Mitochondrial swelling
- Rough endoplasmic reticulum dilation

### Comparison Table: Reversible vs Irreversible Injury

| Feature | Reversible Injury | Irreversible Injury |
| --- | --- | --- |
| **Plasma membrane** | Intact | Ruptured/disrupted |
| **Cell volume** | Increased (swelling) | Decreased (pyknosis) or fragmented |
| **Nucleus** | Normal or slightly pale | Pyknotic, karyorrhectic, or karyolytic |
| **Mitochondria** | Swollen, cristae intact | Amorphous densities, membrane disruption |
| **Reversibility** | Yes, if stimulus removed | No, cell death inevitable |
| **Timeline** | Minutes to hours | Hours to days |

**Clinical Pearl:** Acute tubular necrosis (ATN) in the kidney represents reversible injury in early stages—epithelial cells swell but can regenerate if renal perfusion is restored.

**Warning:** Do not confuse cellular swelling (reversible) with pyknosis (irreversible). Pyknosis indicates nuclear condensation and is a sign of irreversible injury or apoptosis.

Answer

B. Pyknosis of the nucleus

Answer

C. Cell membrane rupture with loss of cellular contents

Answer

D. Fragmentation of the nucleus into membrane-bound fragments

Which of the following morphological changes is characteristic of reversible cell injury?

Explanation

Reversible vs Irreversible Cell Injury

Morphological Features of Reversible Injury

Comparison Table: Reversible vs Irreversible Injury

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Feature	Reversible Injury	Irreversible Injury
Plasma membrane	Intact	Ruptured/disrupted
Cell volume	Increased (swelling)	Decreased (pyknosis) or fragmented
Nucleus	Normal or slightly pale	Pyknotic, karyorrhectic, or karyolytic
Mitochondria	Swollen, cristae intact	Amorphous densities, membrane disruption
Reversibility	Yes, if stimulus removed	No, cell death inevitable
Timeline	Minutes to hours	Hours to days