Flashcards in Cell Injury and Adaption II Deck (18):
Know the difference between necrosis and apoptosis
Know the difference between apoptosis and necrosis as one is more orderly and the other is by accident so more disorderly and makes it difficult for the phagocytes to engulf the dying cell.
What morphological changes take place when a cell is under stress
The limits of adaptive response tested under experimental conditions are often destructive to the cell.
Know in what order does the changes take place in a cell under stress. There's first the cell function that goes down, then there are biochemical changes, then there are ultrastructural changes and then light microscopic changes. Finally we have gross morphologic changes that take place at the organ level.
One thing that is reversible is defects in volume regulation. These are then followed by ATP depletion or interference with production. They cells loose their cation and anion homeostasis which is then followed by ROS damage to the cell membrane or its Na-K pump.
How do you differentiate between damaged mitochondria and irreversible damaged mitochondria
We need to tell the difference between damaged mitochondria and irreversibly damaged mitochondria which can be assessed as the irreversibly damaged mitochondria has Ca influx into them forming dense bodies (due to calcification). This can be detected under the light microscope.
Explain how oxidative stress is handled in a cell
There are superoxides that form in the liver in the process that involves drug metabolism by CP450. Superoxide dismutase gets rid of these super oxide.
H2O2 is removed by catalase or glutathione dismutase.
Also remember that hydroxyl free radicals can form that can damage the cell membrane (remember how they react with archidonic acid in the cell membrane).
Hydroxyl radical causes the most damage in a cell by lipid peroxidation by damaging the cell membrane.
He then went over on how free radical damages the membrane by autocatalytic reaction
Features of reversible cell injury
These consist of the following 5:
1. Cellular swelling
2. Dissociation of ribosomes
3. Plasma membrane blebs
4. Swollen mitochondria
5. Aggregation of nucleolus
Which one of the features of reversible cell injury can we see in a light microscope
Cellular swelling and aggregation of nucleolus
What is an hydropic change? What slide did he show us regarding this?
Hydropic change is an increase in cell volume characterized by large pale cytoplasm and a normally located nucleus. This is usually reversible. This is most often seen in the kidney.
Details about the slide that had hydropic swelling
He then showed us a slide of the kidney with hydropic swelling. Some of the nuclei we cannot see because it is an artifact, all cells in this state have their nuclei in a compact, regular shape.
What is the morphology of irreversible injury
1. The classic thing is eosinophilia which is the binding of eosin to denatured intracytoplasmic proteins.
2. Calcification - that’s how mamogram works, the cells undergo necrosis and calcification and it’s the calcification that is picked up by the radiologists. There are other cells that undergo calcification but its relatively benign.
3. Pyknosis - darkening of the nucleus
4. Karyorrhexis - beginning of the destruction of the nucleus
5. Karyolysis - Ultimate chopping of the DNA and its dissolution
How do you identify Karyorrhexis
DNA is chopped up into large pieces (remember the slide that he showed us)
How do you identify Karyolysis
Dissolving of those big DNA pieces which then look like thin strands. The nuclear membrane was seen to be still intact
Types or morphology of necrosis
1. Coagulative necrosis - the most common kind, it is due to lack of oxygen or hypoxia, it is characterized by the preservation of cell outlines.
2. Caseous necrosis
3. Liquefactive necrosis
4. Fat necrosis
5. Fibrinoid necrosis
Explain coagulative necrosis
We talk in more detail about the coagulative necrosis. This refers to the light microscopic changes in a dead cell or in a dying cell. Just like he said before the most common cause of this is hypoxia. We saw examples of coagulative necrosis in histo lab when we looked at myocardia infarction. Another example is gangerene which is basically dead tissue in the extremities of the body which has arisen due to lack of blood supple. Dry gangrene is usually something that is leather like and the patient has no sensations in it. Wet gangrene is when those dead cells get infected and that part of the body gives a foul odour.
He then showed us a picture of a lung which kind of looks like it has been covered with blue cheese kind of substance. Microscopically it is pink and acellular.
Fat necrosis occurs only in adipose tissue. It normally happens in pancreatitis which involves the release of numerous lipases and proteineases. Liberated fatty acids become saponified to form calcium soaps which appear as amorphous blue in H&E stained tissue sections, often at the periphery of necrotic tissue.
Now we talk about liquefaction necrosis. It occurs when the rate of cell destruction exceeds the rate of repair. This happens in 2 circumstances:
1. Pyogenic (pus-forming) abscesses
2. Hypoxic necrosis of the brain
Once an irreversible injury occurs the cell undegoes
This is the light microscopic hallmark of cell death
Details about caseous necrosis
It is often found with association of mycobacteria. TB has to be ruled out clinically. He then showed us a picture of a lung that kind of looked like its been covered with blue cheese.
Also know how casous necrosis looks like under the microscope. It is pink in color and acellular.