The process of bio decomposition is essential for the maintenance of natural cycles. Decomposition begins from the moment of death, being caused by and autolysis (when the body breaks down its own tissues, usually starting with the liver due to enzymes present, and in the brain due to its high water content), later followed by putrefaction (breakdown of body tissues via bacteria). Prime decomposers are bacteria and fungi but larger organisms also play a role in the process. These range from arthropods such as beetles and flies to larger birds and mammals, such as vultures, dogs and wolves.

During the first few hours following death no signs of corpse decomposition are yet visible. However, the body cools down, usually its temperature dropping by 2 degrees per hour. This is known as algor mortis. Due to gravity blood settles in those parts of the body which are closest to the ground. This is known as livor mortis and it occurs for up to 8 hours following death. Moreover, muscles stiffen as tissue cells in the body can no longer receive oxygen and thus calcium ions cannot be pumped out of muscles. This is known as rigor mortis, and it occurs during the first 12 hours following death. Afterwards, muscles begin to relax due to tissue decay and putrefaction follows.

Putrefaction is associated with the activity of anaerobic bacterial species, which ferment sugars in body tissues, thus producing gases including methane, ammonia and hydrogen sulphate. These accumulate in the corpse and cause it to bloat, predominantly in the abdomen, also adding to any discolouration as haemoglobin in the blood converts to sulfhaemoglobin, making the skin appear green and marbled. The continual buildup of pressure inside the body causes eyes and tongue to protrude and blisters to appear on its skin, and finally the skin loosens and slips off, revealing the decay underneath. In some cases the pressure can also cause the abdomen to burst open, although usually gas is passed out in the same way as it happens in living organisms, as well as through eyes, mouth, etc.
This is the stage at which more microorganisms and larger animals feast on the corpse than in any other stage of decay. For instance, blowflies tend to deposit hundreds of eggs on a corpse, which then hatch within 24 hours, becoming maggots, which grow as they feed on the surrounding flesh. Once they are grown up and nourished enough, they leave their host before turning into blowflies, which then lay their own eggs. And so the cycle repeats itself until the host is entirely consumed. Maggots take full responsibility for corpse consumption if there are no other scavengers present.

It is important to note that the exact decomposition pattern of a specific cadaver is significantly affected by conditions present, including temperature of the environment and presence of wounds on the corpse. Thus, estimating the time of death based purely on insect activity is insufficiently accurate.

Once the stage of putrefaction has ended, only bones and some skin remain. Depending on the temperature of the surroundings, these remains may either dry up and mummify or decompose fully. If all tissues are gone and the skeleton is completely dry, the bones may either get bleached by the sun or damaged by scavenger activity, again depending on environmental circumstances.


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