These notes are to be added to Dr.Karukh’s Cell Injury handout:
Hypoxia results from:
3) Hemoglobin abnormalities (anemia, CO poisoning, methemoglobinemia)
Mechanisms of cell injury (headlines):
1) ATP depletion
2) Accumulation of Reactive Oxygen Species (ROS)
3) Influx of calcium
4) Increased permeability of cellular membranes
5) Mitochondrial damage
6) Accumulation of damaged DNA & misfolded proteins
Patterns of necrosis:
1) Coagulative necrosis: seen in ischemic necrosis of solid organs.
2) Liquefactive necrosis: seen in abscess of solid organs and brain infarcts
3) Fat necrosis: in fatty tissue. Note: calcium appears blue in light microscopy because it likes hematoxylin stain.
4) Caseous necrosis: it is highly characteristic of TB (tuberculosis), but not diagnostic. (90% in TB, 10% in rhinophyma [rosacea])
A caseation is a homogenous eosinophilic acellular material, usually found in the center of a granuloma.
Layers of a caseating granuloma from inside out:
a) Caseation: necrotic tissue [central].
b) 3-4 layers of epitheloid macrophages [activated macrophages with large amount of eosinophilic cytoplasm].
c) 2-3 layers of lymphocytes stimulating the macrophages by cytokines so that they become bigger and more capable of phagocytosis.
5) Gangrenous necrosis: coagulative or liquefactive necrosis of the limbs.
We have two types of irreversible cell injury: apoptosis and necrosis.
Councilman body: is an apoptotic liver cell seen during viral hepatitis.
Q// What is the difference between apoptosis and necrosis?
|1) It involves individual cells.||1) It involves a group of cells.|
|2) It is an active process (energy-requiring).||2) It is a passive process (no energy required).|
|3) It is a clean and regulated process in which the cell is broken down into apoptotic bodies that are removed by macrophages.||3) It is a messy process in which the cell is fragmented. It also disrupts the surrounding tissue.|
|4) There is no inflammatory reaction.||4) It causes an inflammatory reaction.|
|5) The cell size becomes smaller (shrinkage).||5) The cell size becomes bigger by hydropic swelling.|
|6) It is mostly a physiological process, sometimes it becomes pathological.||6) It is always a pathological process.|