The process by which organic materials break down into simpler matter is called decomposition. Shortly after death the body of living organisms starts to decompose. Although no organisms decompose in a similar way they all undergo specific steps of decomposition. There are two forms of decomposition namely abiotic and biotic. Abiotic refers to degradation of a matter through physical or chemical processes, for example hydrolysis. Biotic is the metabolic breakdown of substances by living organisms into simpler components practically by microorganisms.
There are five general stages that describe the decomposition process of vertebrate animals. These processes are namely fresh, bloat, active decay, advanced decay and dry remains. The five stages work hand in hand with the chemical decomposition stages i.e. putrefaction and autolysis.
Immediately after the heart of a living thing stops beating the fresh stage kicks off. In case an individual with cardiopulmonary resuscitation skills happens to be around during death a person can be revived. After the period of death the body starts warming or cooling to march the ambient environment temperature in staged referred to as algor mortis. Between 3-6 hours muscular tissues become rigid and cannot relax at the rigor mortis stage. As there is no more blood circulation around the body it is caused to drain to the dependent body portions due to the gravity force. A bluish-purple discoloration referred to as livor mortis (lividity) is formed.
At this point there is no supply of oxygen or removal of carbon dioxide to and from body tissues. As a result there is decrease in pH which leads to deformity of body cells. Cells therefore release enzymes that are able to start breakdown of surrounding tissues and cells through autolysis. During this stage there are visible changes although sometimes blisters may appear on the body as result of autolysis. Multiplying anaerobic organisms while consuming proteins, lipids and carbohydrates to produce substances like hydrogen sulphide, propionic acid, methane, ammonia and lactic acid. This process is called putrefaction which leads to the bloat stage.
At this stage there is a visual sign that indicated a potential microbial proliferation. Gases accumulation within the body cavity causes a bloated appearance to the cadaver. As a result of the gases, liquids are formed which cause the tissues to be frothy. The formed liquids are force to emanate from natural openings like nose, anus and mouth due to the increased pressure of gases. The pressure might also cause the body to rapture. Haemoglobin is transformed into sulfhemoglobin by intestinal anaerobic bacteria. Sulfhemoglobin circulates through the body giving it a marbled appearance.
If insects have access to the body maggots hatch and start to feed on the tissues. The skin slips and hair detachment occurs as a result of the maggot activity. The ruptured skin allows oxygen to enter into the body which facilitates larvae development and microorganism activities. Odors that are associated to decaying are produced by the purging fluids and gases.
At this stage there is a great mass loss to the body. This loss is as a result of the maggot feeding and purging of the fluid into the environment. A cadaver decomposing island (CDI) is created due to accumulation of purged fluids inside the body. The odors become stronger due to the apparent disintegration and liquefaction of tissues. Migration of the maggots from the body signals the end of active decay.
At this stage severe occurs causing the loss of cadaveric material that was readily available. Insect activity is reduced at this stage. Vegetation death is seen in the surrounding area if the carcass was placed on the ground. There is improved soil carbon and nutrients in the CDI surrounded by carcass. Such nutrients are calcium, magnesium, phosphorus and potassium. There is also a change in pH and soil nitrogen is increased.
Cartilage, bones and dry skins are the only remains of cadaver in this stage. They become bleached and dry if they are exposed to the elements. The cadaver is termed as skeletonised if all soft tissue is removed. If only a few parts of bones are showing the cadaver is partially is skeletonised.
The change in insect fauna visiting over that same period of timeShortly after death insects are attracted to the corpse and they might lay eggs in it. Different kind of insects can be found on decaying body according to Smith (1986). i) necrophagus species which feed on the body, ii)parasites and predators which eat necrophagous species including schizophagus species which feed on the body and turn to predators on later stages, iii) omnivorous species which feed on the body and fellow arthropods e.g. wasps, beetles and ants. The succession through which insects attack the body depend on the condition of carrion decomposition.
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