Pathoma: Cell Injury Flashcards
Injury
occurs when stress exceeds cells ability to adapt
What does the likelihood of injury depend on?
The type and severity of the stress and the type of cell affected
What type of cell is very susceptible to injury?
neurons–>hypoxia
Common causes of injury
inflammation nutritional deficiency or excess hypoxia trauma genetic mutations
Hypoxia
low O2 delivery to tissues
Causes of hypoxia
ischemia
hypxemia
decreased O2 carrying capacity of blood
Ischemia
decreased blood flow through an organ
Why does ischemia occur?
because of a block in an artery or decreased flow of blood through a vein; shock
Bud-Chiari syndrome
thrombosis of the hepatic V.; causes ischemia of liver
due to polycythemia vera or lupus anticoagulant
Polycythemia vera
increase in the number of RBCs–>increased viscosity of blood; leads to Bud Chiari Syndrome
Hypoxemia
low partial pressure of O2 in blood
PaO2 < 60 mm Hg, SaO2 < 90%
PAO2
partial pressure of oxygen in alveolar air space
decreased by increased PACO2 (hypoventilation due to COPD)
SaO2
percent of hemoglobin that has all of its spaces filled with O2
How does decreased O2 carrying capacity occur?
Hb loss or dysfunction
Anemia
decrease in RBC mass
PaO2 normal, SaO2 normal
SaO2 is normal because this number represents % of Hb bound by O2, not how much Hb is available
CO poisoning
CO binds Hb more avidly than O2
PaO2 normal, SaO2 decreased
exposures include smoke from fires and exhaust from cars or gas heaters
Classic finding of CO poisoning
cherry red skin
early sign of exposure is headache; significant exposure can lead to coma and death
Methemoglobinemia
Iron in heme is oxidized to Fe3+, which cannot bind O2
PaO2 normal, SaO2 decreased
seen with oxidant stress (sulfa and nitrate drugs) or in newborns
Classic finding of methemoglobinemia
cyanosis with chocolate-colored blood
treatment is IV methylene blue
helps reduce Fe3+–>Fe2+
What does hypoxia impair?
oxidative phosphorylation
Decreased ATP–>increased Na+ in cell–>increased H2O in cell–>cell swells–>lysis
Is the initial phase of injury reversible?
Yes
hallmark is cellular swelling
leads to loss of microvilli, membrane blebbing, and swelling of RER
Late stages of injury
irreversible damage
hallmark is membrane damamge
plasma membrane–>enzymes will enter the blood
mitochondria–>ETC is disrupted, cytochrome C gets released into the cell cytoplasm
lysosomes–>digests cell instead of things inside the lysosome
End result of irreversible damage of cell
cell death
