T2: Cell Injury Flashcards
What is oncosis?
Pre-lethal changes preceding cell death.
What are the causes of cell injury?
• Hypoxia - lack of oxygen in the area
- Physical agents
- Temperature, trauma, radiation (causes direct damage to DNA). In trauma there is mechanical disruption of the.
- Chemical agents
- Drugs etc. For example paracetamol overdose leads to metabolites binding ti liver cell proteins and lipoproteins.
- Immunologic reactions
- Infectious agents - Toxins and enzymes produced by the bacteria are damaging to the tissue.
- Genetic derangements
- Nutritional imbalances
This is not an exhaustive list.
What are the general biochemical mechanisms of cell injury?
• ATP depletions
• Oxygen and oxygen derived free radicals - free radicals to bind to various things on the cell and destroy things.
• Loss of intercellular calcium haemostasis.
• Defects in membrane permeability - changes to the concentration gradient.
Irreversible mitochondrial damage.
What are the types of cell injury?
Reversible cell injury - shows Cell swelling, pallor, hydropic change (Hydropic changerefers to the accumulation of water in the cell) and vacuolar degeneration. The lack of ATP means the sodium-potassium pump is not working, increasing the amount of sodium in the cell and therefore causing swelling of the cell by osmosis.
Irreversible cell injury - There is leakage of lysosomal enzymes into the cytosol. Also increase of calcium in the call causing the activation of proteins that deaerates the cell. Calcium alongside the cytochrome C leakage, leads to apoptosis.
Reperfusion injury - New damage on reperfusion mediated by free oxygen radicals.
What are the differences between apoptosis and necrosis?
Hint: Think SUMO
Size: Apoptosis leads to cellular shrinkage and only one cell is affected. In necrosis, there is cellular swelling and many cells are affected.
Uptake: In apoptosis cell contents ingested by neighbouring cells and there is no inflammatory response. In necrosis the cell contents are ingested by macrophages and there is significant inflammation.
Membrane: In apoptosis there is membrane blobbing but the integrity remains - apoptotic bodies form. In necrosis there is a loss of membrane integrity and cell lysis occurs.
Organelles: In apoptosis mitochondria release pro-apoptotic proteins and chromatin condensation and there is non-random DNA degeneration. In necrosis there is organelle swelling and lysosomal leakage. There is also Random degeneration of DNA.
What is the most common type of necrosis?
Coagulative necrosis
What is the main cause of caseous necrosis?
Tuberculosis
What are the different types of necrosis?
- Coagulative - The cells retain their outlines and the proteins coagulate and metabolic activity ceases. The predominant method is enzyme degeneration.
- Liquefactive (or Colliquative) - such as in a Bacterial or fungal infection, CNS hypoxia. Seen in the brain. Due to the lack of substantial supporting stroma, the cells all liquify. The main method is enzyme digestion.
- Gangrenous - this is necrosis with putrefaction of the tissue. The cause is mostly infectious or bacterial. The limb (usually) appears black. It can be wet, dry or gas gangrene.
- Caseous - Cheese like structure. It is a structureless form of death. Macrophages cannot fully digest the problem leading to an over reaction.
- Fat necrosis - Due to the leakage of the structure and enzymes being released form the pancreas. It can also be due to trauma. Adipocytes are broken down.
- Fibroid necrosis - It is seen in malignant HTN and autoimmune disease.