â– LECTURE OVERVIEW: Cell injury progresses through a reversible stage before crossing a critical biochemical boundary into irreversible cell injury and cell death.
â– THE CROSSING SEGMENTS:
1. Calcium Accumulation: Depletion of intracellular ATP disables membrane-bound ATP-dependent calcium pumps (Ca2+-ATPase). Calcium rushes into the cytosol and the mitochondria.
2. Enzymatic Overdrive: Elevated cytosolic calcium activates multiple destructive cytosolic enzymes: phospholipases (peroxidizing membranes), proteases (degrading structural cytoskeleton), endonucleases (fragmenting chromatin), and ATPases (further depleting remaining ATP).
3. Heavy Mitochondrial Vacuolization: Mitochondria undergo profound swelling, accumulation of amorphous, calcium-rich dense bodies in the matrix, and permanent loss of membrane potential.
4. Lysosomal Rupture: Low intracellular pH destabilizes lysosomes, releasing acid hydrolases into the cytosol, which digest organelles from within.
5. Nuclear Destruction: Follows a specific sequence: Pyknosis (nuclear condensation), Karyorrhexis (nuclear fragmentation), and Karyolysis (enzymatic disintegration of DNA).
â– SURGICAL LANDMARKS & ANATOMICAL BOUNDARIES:
Intraoperative access requires meticulous dissection along defined tissue planes. Avoid excessive traction near neurovascular bundles and look for key bony landmarks or fascial reflections to secure margins.
â– PHARMACODYNAMIC TARGET ENGAGEMENT:
Receptor binding dynamics dictate the overall speed, duration, and magnitude of physiological responses to therapeutic agents.
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🌟 Dynamic Clinical Key:
The loss of cell membrane permeability is the single most reliable indicator of irreversible injury. This allow tissue-specific intracellular enzymes to leak into systemic circulation where they serve as diagnostic biomarkers: e.g., Cardiac Troponin-I in myocardial infarction, or amylase/lipase in acute pancreatitis. Never divide or ligate any vessel before clearly isolating and confirming its origin and termination. Watch closely for ligand-receptor saturation effects and subsequent tolerance or resistance.