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What 4 things does the degree of injury depend on

- Type of injury
- Severity of injury
- Duration of injury
- Type of tissue


What 7 things can cause cell injury

Chemical agents
Physical agents
Immune mechanisms
Dietary deficiencies/ excesses
Genetic abnormalities


Name 5 physical agents that can cause cell injury

Direct trauma
Extreme temperatures
Pressure changes
Electric currents


Compare Hypoxia and Ischaemia

Hypoxia- Low O2
Ischaemia- Low O2 AND other substances


Compare the 4 types of Hypoxia
Give one example of each

Hypoaxemic Hypoxia: Low O2 in arteries
High altitude

Anaemic Hypoxia: Decreased ability of Hb to carry O2
Anaemia or CO poisoning

Ischaemic Hypoxia: Interruption to blood supply
Vessel blockage

Histiocytic Hypoxia: Unable to use O2, due to disabled Oxidative phosphorylation enzymes
Cyanide poisoning


Explain 2 ways in which immune system can damage the body

- Hypersensitivity reactions: Overly vigorous immune reaction damages tissue

- Autoimmune reactions: Immune system fails to distinguish self from non-self


Which 4 cell components are most susceptible to injury

1. Membranes (Plasma + Organellar)
2. Nucleus (DNA)
3. Proteins (Structural)
4. Mitochondria (Oxidative phosphorylation)


In reversible Hypoxia, explain;

1. Cellular swelling
2. Decreased pH
3. Decreased protein synthesis

Reduced Oxidative phosphorylation-> Reduced ATP

1. Reduced ATP= Reduced Na Pump activity-> Influx of Ca, H2O, Na-> Swelling of cell

2. Reduced ATP= Increased anaerobic glycolysis-> Increased [lactic acid]—> Reduced pH

3. Reduced ATP= Ribosomes detachment-> Reduced protein synthesis


In irreversible hypoxia,

1. How does cytosolic Ca increase
2. Which 4 enzymes are stimulated and what is their effect

1. Enters from Extracellular space, mitochondria, ER

2. ATPase- Reduced ATP

Phospholipase- Less Phospholipids

Protease- Disrupted membrane

Endonuclease- Damages chromatin


Give 5 ways free radicals can be made in the body

1. Normal metabolic reactions
2. Inflammation
3. Radiation
4. Reaction with unbound metals
5. Drugs/ chemicals


How do heat shock proteins protect the cell
Give on example of one of these

When damaged, these proteins ‘mend’ mis-folded proteins and maintain cell viability



What is Ischaemia-Reperfusion injury

Explain 3 causes

If blood flow is returned to a damaged, but not necrotic, damage can be worse than if blood flow wasn’t retuned

Possible causes;

- Increased production of free radicals with reoxygenation
- Increased neutrophil number-> More inflammation and tissue injury
- Delivery of complement proteins


In injured/ dying cells appear under a light microscope in hypoxia, explain the visible changes

1. Cytoplasm swells, becomes more pink and watery

Nucleus shrinks ( Pyknosis)
Nucleus fragments (Karyorrhexis)
Nucleus dissolves (Karyolysis)


In hypoxia, what are the 3 cellular changes in order

1. Cytoplasmic changes
2. Nuclear changes
3. Abnormal cellular accumulations


When looking through an electron microscope, Compare Reversible and Irreversible injury in terms of;

1. Cell membrane
2. ER
3. Ribosomes
4. Mitochondria
5. Nucleus

1. Reversible-Blebs. Irreversible- Myelin figures, defects

2. Reversible- ER Swells. Irreversible- ER Lysis

3. Reversible- Dispersion. Irreversible- Rupture

4. Reversible- Swelling, small densities. Irreversible- Swelling, Large densities

5. Reversible- Chromatin clumping. Irreversible- Shrinking, Fragmenting, Dissolving


Define Oncosis
Define Necrosis
When is necrosis seen

Oncosis: Cell death with swelling, changes prior to death

Necrosis: Morphologic changes in a living organism, after a cell has been dead some tome

- seen after 12 to 24 hours


Name the 4 types of Necrosis
Where do the main 2 types occur, Give 2 examples

Coagulative Necrosis: In solid organs (Heart, Liver)

Liquefactive/ colliquitive Necrosis: In loose tissues (Brain, lungs)

Caseous Necrosis

Fat Necrosis


Define Liquefaction
Compare Coagulative and Liquefactive

Liquefaction= enzymatic digestion

Coagulative: Protein denaturation, Ghost outline of cells remains
Liquefactive: Tissue digestion by enzymes


In caseous necrosis,

1. What is seen under a microscope
2. What it is associated with
3. Appearance by the eye

1. Amorphous debris
2. Infections, especially TB
3. Cheesy


In fat necrosis;

1. Describe the appearance
2. When and how does it occur

1. Melted candle-like
2. Often, acute pancreatitis causes pancreatic lipase release


Define Apoptosis
Does it use ATP
What are the 2 types

Cell death with shrinkage, induced by a regulated intracellular program

Pathological and Physiological


When does Physiological Apoptosis occur
Give 3 examples

1. To maintain a steady-state
2. Hormone controlled involution
3. Embryogenesis


when does pathological Apoptosis occur

1. Graft VS Host disease
2. Damaged cells (Especially DNA)
3. Virus-infected OR Neoplastic cells


Name the 4 visible stages in apoptosis

Normal cell
Shrinkage, chromatin Condensation
Fragmentation/ budding
Apoptic bodies


Name the 3 PHASES in apoptosis

Degradation and Phagocytosis


Compare the 2 mechanisms for apoptosis and which phases they trigger

What do they both result in

Intrinsic- Initiating signal from within cell
Extrinisc- Extracellular initiating signals
Initiation and execution

Activation of caspases (enzymes than mediate apoptosis)


Define Gangrene

Compare Dry and Wet gangrene
What type of necrosis are these

What is Gas gangrene

Necrosis visible to the naked eye

Dry: Necrosis modified by exposure to air- Coagulative Necrosis
Wet: Necrosis modified by infection- Liquefactive Necrosis

Gas: Wet gangrene where the infection is with anaerobic bacteria that produce gas


Define an Infarction
Define Infarct

Infarction: Necrosis caused by reduction in arterial blood flow

Infarct: An area of necrotic tissue which is the result of loss of an arterial blood supply


What are the 2 most common causes of infarction



What is a white Infarct called
Where does it happen
What shape are they

Anaemic Infarct
In solid organs, at end artery
Wedge shaped