General pathology · Cell injury, adaptation and death
Reversible vs irreversible cell injury: the point of no return !
- Mechanism
A hurt cell first swells and can recover; once its mitochondria and membranes are badly damaged, it is past the point of no return and dies.
Updated 2026-11-01
What it is
Early injury is reversible: if the stress stops, the cell returns to normal. Two features mark the point of no return: mitochondria that can no longer make ATP even after blood flow returns, and severe damage to the plasma and lysosomal membranes. After that the cell dies, usually by necrosis, and its proteins leak into the blood, where they are measured as injury markers.
Step by step
- Oxygen falls and oxidative phosphorylation slows; ATP drops.
- The Na⁺/K⁺ ATPase fails: sodium and water enter, and the cell and its ER and mitochondria swell.
- Anaerobic glycolysis uses up glycogen and makes lactic acid; the pH falls and chromatin clumps.
- Ribosomes detach from the rough ER and protein synthesis falls; membrane blebs form. Still reversible.
- Calcium enters and activates phospholipases, proteases and endonucleases; mitochondria open their permeability pore.
- Point of no return: no ATP even if oxygen returns, and plasma and lysosomal membranes rupture.
- Lysosomal enzymes digest the cell, the nucleus disappears and contents leak: necrosis with inflammation.
Signs that separate the two stages
| Feature | Reversible | Irreversible |
|---|---|---|
| Cell volume | Swollen, pale cytoplasm (hydropic change) | Swollen, then broken; deeply eosinophilic |
| Plasma membrane | Blebs, loss of microvilli | Ruptured; contents leak into blood |
| Mitochondria | Swollen, still able to recover | Swollen with dense deposits; cannot make ATP |
| Nucleus | Chromatin clumping | Pyknosis, karyorrhexis, karyolysis |
| Lysosomes | Intact | Rupture and digest the cell |
| Outcome | Recovery if the stress stops | Necrosis (or apoptosis) |
Clinical notes
- Stable angina is reversible myocardial ischemia; infarction is irreversible injury with necrosis.
- Early reperfusion in a myocardial infarction aims to rescue cells that are still in the reversible stage.
In the lab
- Serum troponin rises within hours of myocardial necrosis and is the preferred marker of heart cell death.
- ALT and AST rise when hepatocyte membranes leak; very high values suggest extensive necrosis (ischemic, toxic or viral).
Test yourself
Think of the answer, then tap the question to see it.
What are the two key features of irreversible cell injury?
Inability to restore mitochondrial function (no ATP even after reperfusion) and severe damage to the plasma and lysosomal membranes.
Why does a reversibly injured cell swell?
Low ATP stops the Na⁺/K⁺ ATPase, so sodium and water accumulate inside the cell.
Which nuclear changes indicate cell death?
Pyknosis (shrinking and condensation), karyorrhexis (fragmentation) and karyolysis (fading of the chromatin).
Related
- Mechanisms of cell injury: ATP, mitochondria, calcium, membranes and DNA
- Patterns of necrosis: coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous
- Hypoxia, ischemia and reperfusion injury
- Fatty change (steatosis)
- Apoptosis vs necrosis: the comparison table
Related conditions
- Myocardial Infarction (Heart Attack)
- Stable angina
- Ischaemic stroke
- Transient ischaemic attack
- Acute kidney injury
- Mechanical complications of myocardial infarction
- Rhabdomyolysis
- Acute liver failure
Elsewhere in DurgiPedia
- Cell injury, apoptosis and necrosis
- Organelles: nucleus, ER, Golgi, mitochondria, lysosomes, peroxisomes
- Coronary circulation and myocardial ischemia
- Cardiac troponin as a lab test
- Na⁺/K⁺-ATPase (sodium pump)
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: 4.6 Tissue Injury and Aging (OpenStax (Rice University), 2022); Heart Attack | Myocardial Infarction | MedlinePlus (MedlinePlus, US National Library of Medicine, 2024); Acute Kidney Injury (StatPearls (NCBI Bookshelf), 2024).
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Representative model, for educational purposes only.