Thursday, 9 May 2013

Calcification and Post Mortem Changes

Hello :) In this post I'll explain the processes behind the two types of calcification in tissues. We'll also discuss the changes to a body that are likely to be seen after it has died. 


Calcification is visible grossly as white, chalky areas and may be noted by the gritty or hard texture found on palpation. Under the microscope, calcification is seen as basophilic deposits within cells.

Dystrophic Calcification

The distinguishing feature about dystrophic calcification is that is occurs without hypercalcaemia. It usually appears as local deposits of calcium in dead or injured tissues and is most likely to happen when the blood supply is intact. This form of calcification is an indicator of previous cell or tissue injury. It is rare in liquefactive necrosis.

Examples of dystrophic calcification can be seen in fat necrosis where insoluble calcium soaps form. Another example is in caseous granulomas such as is seen in tuberculosis.

Metastatic Calcification

The defining feature of metastatic calcification is that it occurs with hypercalcaemia. This form of calcification can be seen in primary hyperadrenocorticism. In addition, the most commonly affected areas are the alveolar walls, the gastric mucosa, the kidney tubular epithelial cells and the walls of small blood vessels.

Interestingly any calcified deposit may undergo osseous metaplasia over time.

Post-Mortem Changes

Several factors influence the rate of tissue digestion after death, these are:
o   The ambient temperature: heat leads to rapid decay while cold temperatures prolong the time taken to decay.
o   Insulation: provided by fur, feathers and fat in animals
o   Body temperature: higher body temperatures, such as after physical exercise or a seizure, will result in faster decay. Also an animal’s body temperature may change depending on the time of day. For example, in reptiles their body temperature may be lower at night and higher during the day. 
o   The tissue involved: tissues that naturally have a high amount of enzymes or have a naturally high metabolic rate will autolyse rapidly.
After an animal dies the following changes will occur to its body:
o   The body temperature will drop until it matches the temperature of its environment.
o   The body becomes rigid (this is known as rigor mortis) 3-8 hours after death.
o   Blood collects in the lower parts of the body after putrefaction begins.
o   The rigor mortis disappears after 36 hours
o   Bacterial invasion from the gut occurs via the blood vessels and by direct invasion.
o   Bacteria often produce gas which results in gross distention and bubbles in the tissues
o   Decomposition of the tissues results in the production of foul-smelling gasses (e.g. ammonia, cadaverine.)
o   The tissues turn red, then green, then brown. This is because of the breakdown of haemoglobin and the formation of hydrogen sulphide.
o   Bile leaks from the gall bladder into the surrounding tissues.

 That's all for this series of posts which has covered cell degeneration and death. If you have any questions or comments please feel free to let me know :)


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