Cell Injury

Question 1

What are the causes of cell injury and cell death?

Answer 1

Genetics
Hypoxia
Physical agents
Chemical agents and drugs
Nutrition
Immune mechanisms
Microorganisms

Question 2

What is the difference between hypoxia and ischaemia?

Answer 2

Hypoxia is reduced O2 supply

Ischaemia is reduced blood supply therefore not enough O2, sugar etc.

Therefore ischaemia is worse

Question 3

What are the causes of hypoxia?

Answer 3

– Hypoxaemic hypoxia
– arterial content of oxygen is low
• Reduced inspired p02 at altitude
• Reduced absorption secondary to lung disease

– Anaemic hypoxia – decreased ability of haemoglobin to carry oxygen
• Anaemia
• Carbon monoxide poisoning

– Ischaemic hypoxia - interruption to blood supply
• Blockage of a vessel
• Heart failure

– Histiocytic hypoxia – inability to utilise oxygen in cells due to disabled
oxidative phosphorylation enzymes
• Cyanide poisoning

Question 4

How does hypoxia affect neurones and fibroblasts differently?

Answer 4

Neurones - die within minutes

Fibroblasts - die within few hours

Question 5

How does the immune system damage the body’s cells?

Answer 5

• Hypersensitivity reactions - host tissue is
injured secondary to an overly vigorous immune reaction, e.g., urticaria (= hives)

• Autoimmune reactions - immune system fails to distinguish self from non-self, e.g., Grave’s disease of thyroid.

Question 6

Which cell components are most susceptible to injury?

Answer 6

1. Cell membranes
   Plasma membrane Organellar membranes
2. Nucleus (DNA)
3. Proteins
   Structural (Enzymes)
4. Mitochondria
   - Oxidative phosphorylation