Cell Injury 1

2

nd

class /2021-2022  

Prof. Dr.Nihad N. Hilal

Objectives: What are the



1. Components of normal cell



2. Causes of cell injury



3. General mechanism of cell injury



4. Factors affecting cell response to injury



5. types of cell injury

Components of normal cell

1. Components essential for survival

• Cell membrane maintain intracellular environment
• Nucleus / nucleolus genetic code/ expression
• Mitochondria energy production/storage
• Endoplasmic reticulum/ribosomeprotein synthesis
• Golgi apparatustransport of products of protein 

synthesis

• Lysosomesstorage of hydrolytic enzymes



2. 

Specialized components 

e.g.,

•

Hemoglobin (RBC)

•

Zymogen granules (exocrine cells)

•

Neurofilaments (nerve cells) 

Causes of cell injury

1. Ischemia/hypoxia: 

any 

↓ O

2 

/ ↓ O

2

transport 

(anemia), COPD

1. Infection: viral, bacterial, fungal, parasitic
2. Physical: heat, cold, radiation, electricity
3. Chemical: acid, alkali
4. Immune: 
5. Nutritional
6. Genetic: e.g. enzyme defaccumulation of toxic 

product (iron in hemochromatosis)

General mechanism of cell injury

i. Free radicalsDamage to DNA, proteins, lipid 
ii. ATP depletion
iii ↑ cell membrane permeability 
iv. Influx of calcium Activates enzymes 

* 

Proteases  protein breakdown  

* ATPaseATP depletion; 
* Phospholipases  cell membrane injury; 
* Endonudeases  DNA damage

v. Mitochondrial dysfunction

•

↓ Oxidative phosphorylation

• Release of cytochrome c which trigger apoptosis           

Factors affecting cell response to injury

1.The type of injury
2.The duration of injury
3.The severity of injury
4.The type of injured cell
5.The cells metabolic state
6.The cell’s ability to adapt

Normal cell

Injurious agent

(ischemic, hypoxic, chemical, physical etc)

Irreversible changes

reversible changes

adaptation

Reversible cell injury

Irreversible cell injury

1. Severe membrane damage (influx of Na/water etc)

1. Severe mitochondrial dysfunction: cessation of ATP 

production

3. Rupture of lysosomes release of hydrolytic 

enzymescell lyses

4. Nuclear changes

* pyknosis: condensation chromatin
* karyorhexis: fragmentation of nucleus
* karyolysis: disintegration of nucleus

Cut section of kidney showing cloudy swelling 

note the pale swollen parenchyma

Hydropic degeneration 

cells lining renal tubules distended with water, 

cytoplasm eosinophilic & less granular than normal

Fatty degeneration: grossly liver enlarged, yellow & waxy

Fatty changes: liver: Some hepatocytes filled with fat 

& looks empty due to removal of fat during processing

Dead cells: look to pyknotic faded nuclei

References



Textbook: Kumar V, Abbas AK, Aster JC: Robbins basic 
pathology. 10th edition, Elsevier, 2018.



Currant's  Atlas of Histopathology,4th Revised Edition

Thank you