CELLULAR INJURY Flashcards
What is cellular injury?
Cellular injury occurs when stress exceeds the cell’s ability to adapt.
What factors determine the likelihood of cellular injury?
The type of stress, its severity, and the type of cell affected.
Which cells are highly susceptible to ischemic injury?
Neurons are highly susceptible, while skeletal muscle is more resistant.
What is the difference between slowly developing and acute ischemia?
Slowly developing ischemia (e.g., renal artery atherosclerosis) leads to atrophy, while acute ischemia (e.g., renal artery embolus) leads to injury.
What are common causes of cellular injury?
Inflammation, nutritional deficiency or excess, hypoxia, trauma, and genetic mutations.
What is hypoxia?
Low oxygen delivery to tissues, an important cause of cellular injury.
Why is oxygen essential for cellular function?
Oxygen is the final electron acceptor in the electron transport chain of oxidative phosphorylation.
What happens when oxygen levels decrease?
Decreased ATP production, leading to cellular injury.
What are the main causes of hypoxia?
Ischemia, hypoxemia, and decreased O₂-carrying capacity of blood.
What is ischemia?
Decreased blood flow through an organ.
What are the causes of ischemia?
Decreased arterial perfusion (e.g., atherosclerosis), decreased venous drainage (e.g., Budd-Chiari syndrome), and shock.
What is hypoxemia?
A low partial pressure of oxygen in the blood (PaO₂ < 60 mmHg, SaO₂ < 90%).
What are causes of hypoxemia?
High altitude, hypoventilation, diffusion defects (e.g., pulmonary fibrosis), and V/Q mismatch.
What is a V/Q mismatch?
Blood bypasses oxygenated lung (circulatory problem, e.g., right-to-left shunt) or oxygenated air cannot reach the blood (ventilation problem, e.g., atelectasis).
How does decreased O₂-carrying capacity cause hypoxia?
It occurs due to hemoglobin loss or dysfunction, such as in anemia.
What happens to PaO₂ and SaO₂ in anemia?
PaO₂ remains normal, while SaO₂ remains normal.
What is carbon monoxide (CO) poisoning?
CO binds hemoglobin more avidly than oxygen, leading to decreased SaO₂ but normal PaO₂.
What are common sources of CO exposure?
Smoke from fires, car exhaust, and gas heaters.
What is a classic finding in CO poisoning?
Cherry-red appearance of the skin.
What is an early sign of CO poisoning?
Headache; significant exposure leads to coma and death.
What is methemoglobinemia?
Iron in heme is oxidized to Fe³⁺, which cannot bind oxygen, leading to decreased SaO₂ but normal PaO₂.
What are causes of methemoglobinemia?
Oxidant stress (e.g., sulfa and nitrate drugs) or in newborns.
What are the symptoms of methemoglobinemia?
Cyanosis with chocolate-colored blood.
What is the treatment for methemoglobinemia?
Intravenous methylene blue, which reduces Fe³⁺ back to Fe²⁺.
