A/1. Causes, morphology and mechanisms of cell necrosis.

Question 1

Definition of necrosis

Answer 1

A circumscribed death of cells, tissues and organs in a living patient, followed by acute inflammation.

Question 2

Etiology (causes) of necrosis

Answer 2

1. Oxygen deprivation
2. Chemical agents
3. Infective agents
4. Immunological agents
5. Nutritional imbalance
6. Physical agents
7. Aging

Question 3

1. Oxygen deprivation subtypes

Answer 3

1. Hypoxia

2. Ischemia

Question 4

Hypoxia

Answer 4

• Insufficiency/Reduction of oxygen supply to the tissues.
• More systemic.
• Can be due to reduced oxygen supply, anemia and CO poisoning.

Question 5

Mechanism of hypoxia

Answer 5

Insufficient blood supply to the tissues -> No oxidative phosphorylation -> decreased ATP -> Cell injury

Question 6

Mechanism of hypoxemia

Answer 6

Generalized reduction of oxygen levels in the arterial blood (PaO2 < 60 mmHg) due to

1. Increased altitude
2. Hypoventilation
3. Diffusion defect
4. V/Q mismatch

Question 7

Ischemia

Answer 7

• No supply
• An obstruction or shortage of blood supply to a certain area in a vessel = more localized.
• A more rapid onset
• Neither blood supply nor nutrients
• Due to decreased arterial perfusion, decreased venous drainage, or shock

Question 8

2. Chemical agents

Answer 8

1) Osmotically active particles, like glucose and salt
2) Oxygen in high pressure
3) Poisons that alter the membrane permeability
4) Poisons that disturb homeostatic balance or affect enzymes and cofactors
5) Drugs

Question 9

3. Infective agents

Answer 9

Fungi, bacteria, viruses and their toxins

Question 10

4. Immunological agents

Answer 10

Autoimmune and allergic reactions

Question 11

5. Nutritional imbalance

Answer 11

• Deficiency or excess of nutrients
• E.g. enlargement of fatcells and rupture
• Deficiency of vitamins

Question 12

6. Physical agents

Answer 12

• Trauma
• Poisoning
• Extreme changes in temperature
• Radiation

Question 13

7. Aging

Answer 13

Telomerase activity

Question 14

Morphological features of necrosis

Answer 14

1. Nuclear

2. Non - nuclear

Question 15

1. Nuclear

Answer 15

1. Loss of nucleus = cell death
2. Pyknosis / Karyopyknosis = condensation, irreversible shrinkage of nucleus due to condensation of chromatin into a basophilic mass. Also found in apoptosis.
3. Karyorrhexis = fragmentation
4. Karyolysis = dissolution due to DNAses, RNAses, endonucleases. The cell will stain with eosinophil.

Question 16

2. Non-nuclear

Answer 16

Intake of water/cellular swelling

1. Na+/K+ ATPase pumps stop working.
2. Cells cannot pump out sodium.
3. Osmolarity of the cell increases.
4. Influx of water.

Membrane disintegrity.

Possible calcification. Fatty acids of lipids degraded by phagocytosis may lead to saponification with
extracellular calcium.

Vacuolization: Due to distension of ER due to swelling of cell. Also, there is enzymatic digestion of
organelles.

Cell starts to be more eosinophilic:

1. Acid accumulation of waste in the cells. Acid binds more eosin. Cell becomes more eosinophilic.
2. There is coagulation of denatured enzymes and proteins, which bind eosin.
3. RNA is decreased, reducing basophilia.

Glassy appearance: Reduction in ATP reduces glycogen in cells that store glycogen, reducing glycogen granules in the cytoplasm.

Myelin figures: Phospholipid remnants coming from membrane disintegrity. These are phagocytosed.