General pathology · Cell injury, adaptation and death
Causes of cell injury !
- Topic
Cells are hurt by lack of oxygen, physical forces, chemicals, germs, the immune system, faulty genes, poor nutrition and age.
Updated 2026-11-01
What it is
Cell injury happens when a stress exceeds what a cell can adapt to. The causes fall into a short list of groups, and lack of oxygen (hypoxia) is the most common of all. Knowing the group points to the mechanism (ATP loss, free radicals, membrane damage) and to the pattern of death that follows.
Key facts
- Hypoxia can come from low blood flow (ischemia), low oxygen in the blood (lung disease), low oxygen carriage (anemia, carbon monoxide) or blocked use (cyanide).
- The response to injury depends on the type, duration and severity of the insult.
- It also depends on the cell: neurons and heart muscle tolerate ischemia for minutes; skeletal muscle and fibroblasts for hours.
- The cell’s state matters: nutrition, hormones and genetic variants (for example in drug-metabolizing enzymes) change vulnerability.
The groups of causes, with a classic example
| Group | How it harms | Classic example |
|---|---|---|
| Hypoxia and ischemia | Less oxygen reaches the mitochondria, so ATP falls | Coronary occlusion and myocardial infarction |
| Physical agents | Heat, cold, trauma, electricity and radiation break membranes, proteins and DNA | Burns, frostbite, electrical injury |
| Chemicals and drugs | Direct binding to cell parts or conversion to toxic metabolites | Acetaminophen overdose (liver necrosis) |
| Infectious agents | Toxins, viral take-over of the cell, or the immune attack against them | Viral hepatitis |
| Immune reactions | Antibodies, complement or T cells attack own tissue or harmless antigens | Autoimmune disease, anaphylaxis |
| Genetic defects | Abnormal or missing proteins, misfolded proteins that trigger death | Sickle cell disease |
| Nutritional imbalance | Too little protein, calories or vitamins; or excess (obesity, lipids) | Kwashiorkor |
| Aging | Accumulated DNA damage, worse repair and fewer reserves | Frailty in older adults |
Clinical notes
- In carbon monoxide poisoning pulse oximetry can read falsely normal; carboxyhemoglobin is measured with co-oximetry.
- In Colombia and Latin America, protein-energy malnutrition and infections remain important causes of cell injury in children.
Test yourself
Think of the answer, then tap the question to see it.
What is the most common cause of cell injury?
Hypoxia, most often due to ischemia (reduced blood flow).
Why is ischemia more harmful than hypoxia alone?
Because blood flow also brings glucose and removes metabolites; without it anaerobic glycolysis stops and waste accumulates.
Why can a patient with carbon monoxide poisoning have a normal oxygen tension?
Oxygen dissolves normally in plasma, but carbon monoxide occupies hemoglobin and shifts the curve left, so less oxygen is carried and released to tissues.
Related
- Reversible vs irreversible cell injury: the point of no return
- Mechanisms of cell injury: ATP, mitochondria, calcium, membranes and DNA
- Oxidative stress and free-radical injury
- Hypoxia, ischemia and reperfusion injury
- Chemical (toxic) cell injury: direct and after metabolism
- Patterns of necrosis: coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous
Related conditions
- Carbon monoxide poisoning
- Cyanide poisoning
- Myocardial Infarction (Heart Attack)
- Acetaminophen toxicity
- Burns (thermal, chemical, electrical; inhalation injury)
- Frostbite
- Electrical and lightning injury
- Heat stroke and heat exhaustion
- Viral hepatitis
- Sickle cell disease
- Kwashiorkor
- Marasmus
Elsewhere in DurgiPedia
- Cell injury, apoptosis and necrosis
- The causes of hypoxemia
- Oxygen content, delivery and extraction
- Reactive oxygen species and antioxidants
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); Carbon monoxide poisoning: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2024); Acetaminophen overdose: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2024).
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Representative model, for educational purposes only.