Cell Injury and Death

Overview

Cellular injury occurs dynamically when external stresses profoundly overwhelm cellular adaptive capabilities. Ischemia vastly reduces overwhelmingly the cellular supply of ATP, triggering a catastrophic cascading failure.

Reversible Injury

• Characterized structurally by profoundly intense cellular swelling (hydropic change) precisely due to the strict failure of the energy-dependent Na+/K+ ATPase pump.
• Additionally shows completely reversible detachment of fully functioning ribosomes extensively off the rough endoplasmic reticulum.
• If oxygen or blood flow is restored fully and promptly, the cell totally recovers completely.

Irreversible Injury

Modes of Death

• Apoptosis: Programmed, strictly 'clean' physiological suicide. Uses precisely targeted caspases to cleave DNA exactly cleanly without ever breaking the cell membrane. Consequently, invokes absolutely NO inflammatory response.
• Necrosis: Chaotic, enormously 'messy' pathological explosion. Membrane totally ruptures, relentlessly spilling heavy intracellular enzymes out, massively triggering an explosive inflammatory response.

High Yield Facts

• Karyorrhexis (fragmentation) deeply proves complete necrotic cell death.
• Cytosolic profoundly specific enzymes highly leaking into blood strongly prove necrotic membrane rupture clinically (e.g., extremely high Troponin strictly signifies dying myocardium).