Mechanisms & Causes of Cell Injury

Question 1

What is autolysis?

Answer 1

Self digestion due to endogenous enzymes

Question 2

What is bile imbibition?

Answer 2

Postmortem leakage of bile from the gallbladder

Question 3

Normal Cells

Answer 3

Homeostasis steady state is determined by:
- State of metabolism, differentiation, and specialization
- Constraints of neighboring cells
- Availability to metabolic substrates
- Have the ability to adapt to changes in physiologic states
New steady states achieved→ cell survival → continued function

Question 4

4 Adaptive Responses

Answer 4

Hypertrophy

• Increase in cell size

Hyperplasia

• Increase in cell number

Atrophy

• Decrease in cell size and metabolic activity

Metaplasia

• Change in cell phenotype
• Ex. tracheal columnar epithelial cell changes to a squamous epithelial cell

Elimination of added stress = cell returns to normal state without negative consequences

Question 5

What is cell injury?

Answer 5

Something that disrupts cellular homeostasis

• Injury if limits of adaptive responses are exceeded
• Injury if exposed to injurious agents
• Injury if deprived of required nutrients
• Injury via mutations that affect cellular constituents
  
  • Ex. Neoplasia, Heritable diseases

Question 6

Consequences of Cell Injury:

2 Options

Answer 6

2 options:

• Reversible injury
  
  • Functional & morphologic changes that occur with injury are reversible up to a certain point
  • The cell can “restore” itself/return back to homeostasis
  • Damage from stimulus can be fixed
• Irreversible Injury
  
  • If stimulus persits or is severe enough from start →
  • Cell suffers irreversible cell injury →
  • Cell death

Line between reversible & irreversible is blurry

Question 7

Causes & Mechanisms of Cell Injury

Answer 7

Causes:

• Numerous & diverse
• Intrinsic & extrinsic

All causes activate 1+ of four common final mechanisms that lead to cell injury:

• ATP depletion
• Permeabilization of the cell membrane
• Disruption of biochemical pathways
• Damage to DNA

Question 8

Mechanisms of Cell Injury: ATP Depletion

Answer 8

ATP required for all anabolic/catabolic processes within cell:

• Membrane transport
• Protein synthesis
• Lipogenesis
• Reactions for phospholipid turnover

Question 9

Under ischemic conditions (low O2), what effect does ATP depletion have on the cell?

Answer 9

Under ischemic conditions (Low O2):

Decreased function of Na+/K+ ATPase→

• Increased intracellular Ca2+ = damage to cell
• Increased intracellular Na+ = influx of H2O
• Increased loss of K+ from cell

All lead to cell swelling