What are the stages of death?
Stages of death:
What is pallor mortis?
Pallor mortis: Pale, heart Is no longer pumping. Blood is no longer moving through tissues.
What is algor mortis?
Algor mortis: Chilled, loss of heat in the body.
What is rigor mortis?
Rigor mortis: Body becomes stiff
What is livor mortis?
Livor mortis: Pooling of blood, on whatever the down side of that animal or body is
Blood, or blood-tinged fluid, will pool on the gravity-dependent side
What's the timeline for Decomposition/Skeletonization?
Less well defined time frame for the rest, depending on environmental conditions
What is postmortem autolysis?
Postmortem autolysis is:
A type of cell death that's similar to necrosis, but occurs upon death of the animal ONLY
Fluids move, gravity dependent vs being pumped by the heart
Postmortem autolysis + bacteria = ?
Postmortem autolysis + bacteria = putrification
Which cell type would undergo cell death faster: a neuron or a fibrocyte?
A neuron is more delicate, and therefore would undergo cell death and degeneration faster than a fibrocyte.
What's another term for livor mortis?
Hypostatic congestion is another term for livor mortis. Instead of the body/heart pumping fluids, fluid movement is dependent on gravity.
How would proximity to the GI tract effect postmortem autolysis?
The closer in proximity you are to the gi tract, and therefore to the gut flora, the more readily accessible the bacteria are to make a mess of things.
Even through the body dies, the bacteria do just fine. There are no neutrophils, no maintenance of pH to stop the bacteria.
What are the two types of temperature to be aware of, when considering factors in postmortem autolysis?
Internal temperature - can be variable at the time of death, if the animal had a fever, etc. An increased internal temperature would increase the speed at which PMA takes place.
Ambient temperature - Environmental temperatures. Hot day in summer? Great news for PMA, bad news for necropsy. Ambient temperatures will have some effect on the overall temperature of the carcass, depending on how large it is.
On a cell death timeline, what are some scenarios you could see if you have a cell injury and then death follows shortly thereafter?
On a cell death timeline, if you have a cell injury and then death follows shortly thereafter...
- You may have cell injury, resulting in the whole body dying. If death occurs rapidly, after that cell injury, you'll see one thing, (She didn't clarify one this one thing was; I assume a singular disease process that lead to death.)
- If just that one cell dies, or is undergoing early necrosis, you may or may not see a gross lesion. But you probably will see a histologic lesion.
- Let's say you've had a cell injury, the animal dies, and the necropsy is done right away. The tissues are put into fixation right away... You should be able to see the subtle, or early histologic lesions.
On a cell death timeline, what are some scenarios you could see if you have a cell injury and then death follows much later?
On a cell death timeline, if you have a cell injury and then death follows much later, you could see:
- The cell injury occurs, but the body doesn't die right away. This duration of time will result in a different appearance of that cellular change than if the animal died right away. It may not be dramatic, but it will be a different spectrum of change.
- If there's injury to the cell and the cell undergoes necrosis, but the animal dies later on, you probably will see a both a gross lesion and the histologic lesion.
- On the other hand, the animal dies, and then the necropsy isn't able to be done until 2+ days later, it maybe be very hard to see those lesions due to autolysis.
There's always a timeline in place; The clock starts ticking as soon as that animal dies. Cooling will slow decay down, but won't stop it.
What are some general signs of necrosis?
- Local color change at the area of cell death. Most forms of necrosis are pale, unless hemorrhage is involved.
- Necrosis is well demarcated, isolated areas. You could see a hyperemic zone, or fibrosis.
- Calcification may (or may not) be present
- You will potentally see inflammation, +/- bacteria.
Essentially, with necrosis, you'll see signs that the body was reacting to the death of the cells. A zone of hyperemia, inflammation, calcification... These are all changes that take place in a body, when the body is alive to react. You won't see these changes with autolysis.
What are some general signs of autolysis?
- More uniform color changes, typically diffuse. Could be pale or dark, and lividity will be present
- No vascular patterns to lesions, because the body was no longer responding
- No calcification
- No inflammation
- Because the body isn't responding with inflammation/neutrophils, you'll see Cadaver bacilli
What are some ways you can reduce postmortem autolysis?
To reduce postmortem autolysis, you can:
- Minimize the duration between death and necropsy
- Cool the carcass quickly (but don't freeze it!)
- Fix the specimen, in buffered neutral formalin
What are some specific examples of when you'd really want to minimize the time between death and necropsy?
Some specific examples of when you'd really want to minimize the time between death and necropsy:
- Research cases.
- Neuro, GI, Respiratory cases - You rapidly lose the ability to see the specific lesion in these tissues. They degenerate faster than others.
- Legal/Insurance cases - Herd health, or has a potential impact on human health? Do the necropsy immediately.
When cooling the body to reduce PMA, what are some influences on body temperature after death?
Some influences on body temperature after death:
- Fever/seizures - The animal's internal body temp will be high, and will take longer to cool down.
- High percentage of body fat - Well insulated, therefore will take longer to cool down
- Wool or long hair - again, well insulated, longer to cool
- Large vs. Small body size - A Larger animal will take longer to cool vs smaller
What is the ideal size, when fixing tissues in buffered neutral formalin?
The tissue needs to be no larger than 0.5 cm in thickness.
Buffered neutral formalin prevents us from getting acid hematin, a black granular material that we'll see from time to time. (She mentioned this in passing, probably not important)
What's the perk of breadloafing?
Breadloafing a specimen allows you to fix a larger sample, which maintaining orientation of the specimen.