Cell Injury and Necrosis

Question 1

What is the definition of infarction?

Answer 1

Death of tissue due to loss of blood supply, most often as a result of arterial occlusion

Question 2

List 4 causes of cell injury

Answer 2

1. Hypoxia/anoxia – lack of oxygen impairing cellular metabolism (lack of ATP produced in mitochondria)
2. Microbial infection
3. Drug/toxin induced injury
4. Physical trauma – burns, radiation

Question 3

What occurs in ‘reversible’ cell injury?

Answer 3

ATP depletion leads to failure of ion pumps in cell membranes so that the cell and its organelles become swollen

Question 4

What occurs in ‘irreversible cell injury?

Answer 4

• Cell membranes breakdown
  
  • Protein synthesis fails - energy dependent process, lose energy, lose protein synthesis
  • Nuclear and cytoplasmic contents undergo dissolution

Question 5

What is a ‘Ghost’ cell

Answer 5

A dead cell in which the outline remains visible, but whose nucleus and cytoplasmic structures are not stainable.

Question 6

What are 4 hallmarks of cell necrosis?

Answer 6

• Mitochondrial damage: decreased ATP and increased ROS
• Entry of Ca2+: increase mitochondrial permeability, activate cellular enzymes
• Membrane damage: Plasma membrane = loss of cellular components, Lysosomal membrane - enzymatic digestion of cellular components
• DNA damage, activation of pro-apoptotic proteins

Question 7

What nuclear changes occur in necrosis?

Answer 7

• basophilia of chromatin may fade due to loss of DNA because of enzymatic degradation by endonucleases = KARYOLYSIS
• nuclear shrinkage and increased basophilia = PYKNOSIS
• nuclear fragmentation = KARYORRHEXIS
• complete nuclear dissolution

Question 8

How is necrosis identified histologically?

Answer 8

• Increased cytoplasmic eosinophilia (more intense pink staining with the eosin component of the H&E stain): caused by increased eosin binding to damaged protein and loss of rRNA

Question 9

What are the different types of necrosis and what are some clinical examples?

Answer 9

• Coagulative necrosis: typically seen in solid organ except for the brain eg. Ischemic heart disease
• Caseous necrosis eg. TB in the lung
• Liquefactive necrosis eg. cerebral infarction

Question 10

How does apoptosis differ from necrosis?

Answer 10

• energy dependent process, ‘regulated’
• only single cells affected
• apoptotic bodies
• functionally intact cell membrane
• phagocytosis by macrophages

Question 11

What is the difference between dystrophic and metastatic calcification?

Answer 11

Dystrophic is calcium phosphate deposits due to membrane damage, metastatic is in normal tissues in the context of hypercalcemia