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Thread: A Question

  1. #1 A Question 
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    I realise that this may sound a little odd, but what exactly enables decomposition? By this I mean, why is it that we decompose only after death and not before?


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  3. #2  
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    Decomposition is a microbial process (fungi and some bacteria and archaea.) We can fight off microbes with natural defences - things liks physical barriers, chemical barriers, and the immune system.

    Some diseases such as leprosy get past this, and begin decomposition of living tissue.


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    Things like venoms can actually induce things like necrosis as well- if you localize the venom of various snakes, it can cause holes to be eaten through the area in question.

    So there can be mitigating biological factors as well, aside from just bacteria 'getting around' the usual defensive lines, impacting decay.
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  5. #4  
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    Also important is the fact that biological molecules are inherently unstable - they tend to spontaneously breakdown (decompose) quite readily. Without continual maintenance and replenishment, much of the stuff that you are made from will breakdown into a gooey mess, or in scientific terms, "putrefy". Obviously, a whole bunch of other things are going on too (see other posts).

    The BBC has a rather macabre article on the topic.
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  6. #5  
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    Thank you all for your replies.
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    One of the points I did not see addressed here is the lack of oxygen. The earliest stage of post mortem decomposition is autolysis of the cells due to oxygen deprivation. This is followed by skin slip, when the connections holding the skin attached to the body start breaking down, followed by putrefaction, when the bacteria get into action. Even in the absence of bacteria though [as in intrauterine death], there is maceration of the fetus [darkening of skin, loss of anatomical features]. The most obvious c.o.d. in such cases is usually an interrupted blood flow [ie oxygen] due to a compromised umbilical cord.


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    I had an entomology prof that helped a few times with maggot ID. Apparently they can show you how long a corpse has been dead, given the temperature etc, based on what species it is. There is a predictable progression in maggots but the one catch is that you have to rear them to adult stage to get anything close to a positive ID!
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  9. #8  
    Forum Masters Degree samcdkey's Avatar
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    Sorry if this sounds like a stupid question, but why would you want to ID a maggot?

    [P.S. This is not my field but I find this stuff especially interesting after watching Grisham in CSI:Vegas]
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    well, there is a progression of colonization of the corpse. Certain species hit up the body at certain times. So, if you find a human corpse and you want to know when it died (for forensic reasons), obviously getting as close to time of death as possible is best. Now, saying it "looks waxy and smells like cheese, also there is purge fluid" doesn't always cut it, especially in the summer when maggots are aplenty.

    Maggots, once you get to species, can very easily be observed to know how old they were when you found them. If you know the species, you can know how many instars (or sheds) they are into development. This is critical, because timelimes on common species have mostly been worked out. So you can see how long the maggots have been there and know when the fly likely laid eggs; flies are attracted to different scents predominantly. Also, maggots can and will outcompete other maggots given food available (ie what is rotting) and depending on conditions.

    So, if you know what stage the maggot is at and you know when the flies usually lay their eggs after death in given conditions (as indicated by prevalence of species; most are a monospecies population or close to it), you can tell when the person died usually to within a day or so. I'd say that is forensically important at a murder scene that is weeks old, wouldn't you?

    also it wasn't a stupid question .
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