[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Histology](https://durgical.com/en/histology/) › [The cell](https://durgical.com/en/histology/#a-cell) › Cell injury, apoptosis and necrosis

[Histology](https://durgical.com/en/histology/) · [The cell](https://durgical.com/en/histology/#a-cell)

# Cell injury, apoptosis and necrosis

- Process

A damaged cell can recover, die in an orderly way (apoptosis) or die in a messy, inflammatory way (necrosis).

Updated 2026-11-01

**See it in 3D:** [Liver](https://durgical.com/en/anatomy/liver/)

## Key points

- Apoptosis = a single cell that shrinks, no inflammation; necrosis = a group that swells, with inflammation.
- Coagulative (infarct, except brain), liquefactive (brain, abscess), caseous (tuberculosis), fat (pancreas).
- BCL-2 is anti-apoptotic; it is overexpressed through t(14;18) in follicular lymphoma.
- Nuclear changes: pyknosis (shrinking), karyorrhexis (fragmenting), karyolysis (fading).

## What it is

Faced with an insult (lack of oxygen, toxins, infection), a cell first shows reversible changes; if the damage persists, it dies. Apoptosis is programmed, orderly death without inflammation; necrosis is accidental death with burst membranes and inflammation. The pattern of necrosis points to the cause.

## Key facts

- Coagulative necrosis: the outlines of cells remain but nuclei are lost; typical of myocardial and renal infarcts.
- Liquefactive necrosis: the tissue turns liquid; typical of brain infarcts and abscesses.
- Caseous necrosis: amorphous granular «cheese-like» material inside granulomas; typical of tuberculosis.
- Fat necrosis: lipases release fatty acids that bind calcium (saponification); typical of acute pancreatitis.
- Fibrinoid necrosis: bright pink deposits in vessel walls in vasculitis and malignant hypertension.

## Step by step

- Insult: hypoxia, toxins, radiation, microbes or immune attack.
- Reversible injury: the sodium pump fails, water enters, the cell swells and blebs; fatty change may appear.
- If the damage goes on: membranes are injured, calcium floods in and lysosomes burst.
- Intrinsic apoptosis: BAX/BAK proteins release cytochrome c from the mitochondrion; BCL-2 prevents it.
- Extrinsic pathway: Fas ligand or TNF activates death receptors and caspase 8.
- Executioner caspases break the cell into apoptotic bodies that macrophages eat without inflammation.

## Apoptosis versus necrosis

| Feature | Apoptosis | Necrosis |
| --- | --- | --- |
| Extent | Single cells | Groups of cells, areas of tissue |
| Cell size | Shrinks | Swells |
| Nucleus | Pyknosis and karyorrhexis; apoptotic bodies | Pyknosis, karyorrhexis and karyolysis |
| Membrane | Intact; blebs that break off | Ruptured; contents spill into the tissue |
| Inflammation | No | Yes |
| Examples | Embryonic development, hormone withdrawal, cytotoxic T cells, Councilman bodies in hepatitis | Infarct, abscess, tuberculosis, pancreatitis |

## In the lab

- On H&E an apoptotic cell is small, with very eosinophilic cytoplasm and a dense or fragmented nucleus, sometimes with a clear halo around it.
- In a recent myocardial infarct the fibres look more eosinophilic and lose their nuclei, and neutrophils arrive within the first days.

## Memory aid

Apoptosis leaves quietly; necrosis bursts and calls in the neutrophils.

## Test yourself

Think of the answer, then tap the question to see it.

## Which type of necrosis is seen in a brain infarct?

Liquefactive necrosis, because brain tissue has few structural proteins and many enzymes.

## Which released mitochondrial protein triggers the intrinsic pathway of apoptosis?

Cytochrome c, which builds the apoptosome and activates caspase 9.

## Which type of necrosis is typical of tuberculosis?

Caseous necrosis: granular, eosinophilic, amorphous material in the centre of the granuloma.

## Why does apoptosis not cause inflammation?

The membrane stays intact and apoptotic bodies are eaten before their contents leak out.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/histology/cell-injury-apoptosis-and-necrosis/)

## See it in 3D

The structures of Durgical's 3D anatomy where it is found.

- [Liver](https://durgical.com/en/anatomy/liver/)

## Related

- [Organelles: nucleus, ER, Golgi, mitochondria, lysosomes, peroxisomes](https://durgical.com/en/histology/organelles-nucleus-er-golgi-mitochondria-lysosomes-peroxisomes/)
- [Cell adaptations: hypertrophy, hyperplasia, atrophy, metaplasia](https://durgical.com/en/histology/cell-adaptations-hypertrophy-hyperplasia-atrophy-metaplasia/)
- [Cell cycle, mitosis and meiosis](https://durgical.com/en/histology/cell-cycle-mitosis-and-meiosis/)
- [Wound healing: phases and scar](https://durgical.com/en/histology/wound-healing-phases-and-scar/)

## Related conditions

- [Myocardial Infarction (Heart Attack)](https://durgical.com/en/conditions/myocardial-infarction/)
- [Ischaemic stroke](https://durgical.com/en/conditions/ischaemic-stroke/)
- [Pulmonary tuberculosis](https://durgical.com/en/conditions/pulmonary-tuberculosis/)
- [Acute pancreatitis](https://durgical.com/en/conditions/acute-pancreatitis/)
- [Viral hepatitis](https://durgical.com/en/conditions/viral-hepatitis/)

## Microorganisms

- [Mycobacterium tuberculosis](https://durgical.com/en/microbiology/mycobacterium-tuberculosis/)

[← All of histology](https://durgical.com/en/histology/)

Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.

Sources: [4.6 Tissue Injury and Aging](https://openstax.org/books/anatomy-and-physiology-2e/pages/4-6-tissue-injury-and-aging) (OpenStax (Rice University), 2022); [What Is Cancer?](https://www.cancer.gov/about-cancer/understanding/what-is-cancer) (National Cancer Institute, 2021).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/histology/cell-injury-apoptosis-and-necrosis/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/histology/cell-injury-apoptosis-and-necrosis/