1️⃣ Reversible vs irreversible injury

Question 1

What factors determine if injury is reversible?

Answer 1

Cell-specific (genetics, type, adaptability, pre-existing conditions) and injury-specific (type, duration, severity).

Question 2

Describe reversible injury morphology.

Answer 2

Light microscopy: cell swelling (ER, mitochondria), fatty change; ultrastructure: membrane blebs, chromatin clumping, ER/mitochondrial density changes.

Question 3

Describe irreversible injury morphology.

Answer 3

ER/mitochondrial swelling, ribosome detachment, lysosome rupture, mitochondrial densities, nuclear condensation/fragmentation, membrane breakdown → inflammation.

Question 4

What thresholds mark irreversible injury?

Answer 4

Loss of mitochondrial ATP production and loss of membrane integrity (plasma, lysosomal, mitochondrial).

Question 5

Explain haematoxylin & eosin staining.

Answer 5

Haematoxylin stains basophilic (nuclei) purple-blue; eosin stains acidophilic (cytoplasm) pink-red.

Question 6

Give other histological stains.

Answer 6

Triphenyltetrazolium chloride for viable myocardium (magenta), DAPI for nuclear DNA.

Question 7

What causes and results from ATP depletion?

Answer 7

Caused by ↓ O₂/nutrients, toxins; leads to Na⁺/K⁺ pump failure (swelling), ↑ anaerobic glycolysis (↓ pH, chromatin clumping), ribosome detachment (↓ protein synthesis → apoptosis).

Question 8

What causes and results from mitochondrial damage?

Answer 8

Caused by ↑ Ca²⁺, ROS, lipid peroxidation; results in ↓ ATP, cytochrome c release (apoptosis).

Question 9

How does calcium influx injure cells?

Answer 9

ATP pump failure → ↑ intracellular Ca²⁺ → activates proteases, phospholipases, caspases → necrosis/apoptosis.

Question 10

How does ROS accumulation injure cells?

Answer 10

Excess ROS → lipid peroxidation (membrane damage), protein modification (dysfunction), DNA damage (mutations, strand breaks → apoptosis).

Question 11

Describe membrane damage consequences.

Answer 11

Plasma membrane leaks (swelling, inflammation), mitochondrial membrane dysfunction (↓ ATP), lysosomal rupture (autodigestion).

Question 12

What are sources and results of protein/DNA damage?

Answer 12

Caused by ROS, toxins, radiation; results in misfolded proteins (ER stress) and DNA breaks (apoptosis if unrepaired).

Question 13

Compare necrosis and apoptosis.

Answer 13

Necrosis: swelling, membrane rupture, inflammation; Apoptosis: shrinkage, intact membrane, apoptotic bodies, no inflammation.