What is a cellular injury?
o When a cell exits it’s normal balance (homeostasis) as a result of
excessive demand, inadequate response.
How do cellular injuries occur?
o Membrane damage
o Inhibition of aerobic respiration
o Inhibition of protein synthesis
o Modification of genetic apparatus
What is the cellular response to injury?
o The cells are forced into an adaptive state with new homeostasis
o Alterations in morphology occur:
Hypertrophy: increase in the size of the cells (e.g during
mitral valve stenosis you have hypertrophy of the walls of
the heart to generate a contractile force)
Hyperplasia: increase in the NUMBER of cells
Atrophy: Shrinkage of the cell due to loss of substances
Metaplasia: reversible change between cell types
How is reversible injury different than adaptation?
o Loss / compromise of function
o Reduction in the response
o Reversibly injured cells are more prone to more injury
What are the characteristics of reversible injury (ischemia)?
o Contraction of mitochondria due to reduced O2 causes fluid
movement into the space that would have been occupied by the
ATP generated. Therefore there is a LOW AMPLITUDE SWELLING
o Fall in ATP stimulates glycolysis which then leads to the los of
PAS+ reactivity (therefore you see lower PAS+ staining). This also
leads to fall in pH due to anaerobic respiration.
o Cellular swelling: due to the fact that ion pumps are disrupted.
Fluid accumulates in RER and causes clear fluid vaculus. CLOUDY
APPEARANCE. This affects:
Membrane stability
Ion-pumps
ATP generation
Intracellular pressure causes cells to swell
o RER fragments due to ischemia and therefore DECREASES
PROTEIN SYNTHESIS
o Fatty change occurs due to accumulation of lipid. This creates large
vacuolues that displace the nucleus
o Change in shape + loss of membrane specialization. Ca2+ increases
intracellularly and leads to many disturbances
What are the characteristics of irreversible injury (necrosis)?
o High amplitude swelling and rupture leads to calcification
o When a cell exits it’s normal balance (homeostasis) as a result of
excessive demand, inadequate response.
How do cellular injuries occur?
o Membrane damage
o Inhibition of aerobic respiration
o Inhibition of protein synthesis
o Modification of genetic apparatus
What is the cellular response to injury?
o The cells are forced into an adaptive state with new homeostasis
o Alterations in morphology occur:
Hypertrophy: increase in the size of the cells (e.g during
mitral valve stenosis you have hypertrophy of the walls of
the heart to generate a contractile force)
Hyperplasia: increase in the NUMBER of cells
Atrophy: Shrinkage of the cell due to loss of substances
Metaplasia: reversible change between cell types
How is reversible injury different than adaptation?
o Loss / compromise of function
o Reduction in the response
o Reversibly injured cells are more prone to more injury
What are the characteristics of reversible injury (ischemia)?
o Contraction of mitochondria due to reduced O2 causes fluid
movement into the space that would have been occupied by the
ATP generated. Therefore there is a LOW AMPLITUDE SWELLING
o Fall in ATP stimulates glycolysis which then leads to the los of
PAS+ reactivity (therefore you see lower PAS+ staining). This also
leads to fall in pH due to anaerobic respiration.
o Cellular swelling: due to the fact that ion pumps are disrupted.
Fluid accumulates in RER and causes clear fluid vaculus. CLOUDY
APPEARANCE. This affects:
Membrane stability
Ion-pumps
ATP generation
Intracellular pressure causes cells to swell
o RER fragments due to ischemia and therefore DECREASES
PROTEIN SYNTHESIS
o Fatty change occurs due to accumulation of lipid. This creates large
vacuolues that displace the nucleus
o Change in shape + loss of membrane specialization. Ca2+ increases
intracellularly and leads to many disturbances
What are the characteristics of irreversible injury (necrosis)?
o High amplitude swelling and rupture leads to calcification
