Decomposition

From Freepedia

(Redirected from Rotting)
For other uses, see Decomposition (disambiguation).

Parts of this article may have been copied fromhere. This constitutes plagiarism and should ideally be replaced with information gathered from a range of sources.

This article is in need of attention.
You can help Wikipedia by editing it into a better article.
Please also consider changing this notice to be more specific.
Image:Rotting fruit.jpg

Decomposition is the reduction of bodies and other formerly living organisms into simpler forms of matter and, most particularly, to the fate of the human body after death. The science which studies decomposition generally is called taphonomy.

A body will begin to decompose shortly after death. Decomposition can be simplified in two stages: In the first stage, human decomposition is limited to the production of vapors. In the second stage of human decomposition, fluidic materials form and the flesh begins to decompose.

Historically, the progression of human decomposition has been described as taking place in four stages: fresh (autolysis), bloat (putrefaction), decay (putrefaction and carnivores) and dry (diagenesis).

Warning: Some of the images in this article are extremely graphic. Please be cautioned

Contents

Constituent factors

The rate and the manner in which a human or animal body decomposes is strongly affected by a number of factors. In a roughly descending degree of importance, those factors include:

Decomposition process

Signs of Death

Algor mortis Rigor mortis Livor mortis Decomposition

Decomposition begins at the moment of death. At this stage it is caused by two factors: autolysis, the breaking down of tissues by the body's own internal chemicals and enzymes; and putrefaction, the breakdown of tissues by bacteria. These processes release gases that are the chief source of the characteristic odour of dead bodies. These gases swell the body.

Scavengers play an important role in decomposition. Insects and other animals are typically the next agent of decomposition, assuming the body is accessible to them. The most important insects that are typically involved in the process include the fleshflies (Sarcophagidae) and blowflies (Calliphoridae). The green-bottle fly seen in the summer is a blowfly. Larger scavengers, including coyotes, dogs, wolves, foxes, rats, and mice may eat a body if it is accessible to them. Some of these animals will also remove and scatter bones.

Initial Decay

Stage 1

Time Frame: 0-3 days after death

Although the body shortly after death appears fresh from the outside, the bacteria that before death were feeding on the contents of the intestine begin to digest the intestine itself. Eventually, they break out of the intestine and start digesting the surrounding internal organs. The body's own digestive enzymes (normally in the intestine) also spread through the body, contributing to decomposition.

On an even smaller scale, enzymes inside individual cells are released when the cell dies. These enzymes break down the cell and its connections with other cells.

Insect Activity From the moment of death flies are attracted to bodies. Without the normal defences of a living animal, blowflies and house flies are able to lay eggs around wounds and natural body openings (mouth, nose, eyes, anus, genitalia). These eggs hatch and move into the body, often within 24 hours. The life cycle of a fly from egg to maggot to fly takes from two to three weeks. It can take considerably longer at low temperatures.

Putrefaction

Stage 2

Time Frame: 4-10 days after death

Bacteria break down tissues and cells, releasing fluids into body cavities. They often respire in the absence of oxygen (anaerobically) and produce various gases including hydrogen sulphide, methane, cadaverine and putrescine as by-products. People might find these gases foul smelling, but they will attract a large variety of insects.

The build up of gas resulting from the intense activity of the multiplying bacteria, creates pressure within the body. This pressure inflates the body and forces fluids out of cells and blood vessels and into the body cavity.

Insect Activity The young maggots move throughout the body, spreading bacteria, secreting digestive enzymes and tearing tissues with their mouth hooks. They move as a maggot mass benefiting from communal heat and shared digestive secretions.

The rate of decay increases, and the smells and body fluids that begin to eminate from the body attract more blowflies, flesh flies, beetles and mites. The later-arriving flies and beetles are predators, feeding on maggots as well as the decaying flesh. They are joined by parasitoid wasps that lay their eggs inside maggots and later, inside pupae.

Black Putrefaction

Stage 3

Time Frame: 10-20 days after death

Image:BlackPutrefaction.jpg

The bloated body eventually collapses, leaving a flattened body whose flesh has a creamy consistency. The exposed parts of the body are black in colour and there is a very strong smell of decay.

A large volume of body fluids drain from the body at this stage and seep into the surrounding soil. Other insects and mites feed on this material.

The insects consume the bulk of the flesh and the body temperature increases with their activity. Bacterial decay is still very important, and bacteria will eventually consume the body if insects are excluded.

Insect Activity By this stage, several generations of maggots are present on the body and some have become fully grown. They migrate from the body and bury themselves in the soil where they become pupae. Predatory maggots are much more abundant at this stage, and the pioneer flies cease to be attracted to the corpse. Predatory beetles lay their eggs in the corpse and their larvae then hatch out and feed on the decaying flesh. Parasitoid wasps are much more common, laying their eggs inside maggots and pupae.

Butyric fermentation

Image:DecomposedWoman.jpg

Stage 4

Time Frame: 20-50 days after death

All the remaining flesh is removed over this period and the body dries out. It has a cheesy smell, caused by butyric acid, and this smell attracts a new suite of corpse organisms.

The surface of the body that is in contact with the ground becomes covered with mould as the body ferments.

Insect Activity The reduction in soft food makes the body less palatable to the mouth-hooks of maggots, and more suitable for the chewing mouthparts of beetles. Beetles feed on the skin and ligaments. Many of these beetles are larvae. They hatch from eggs, laid by adults, which fed on the body in earlier stages of decay.

The cheese fly consumes any remaining moist flesh at this stage, even though it is uncommon earlier in decay.

Predators and parasitoids are still present at this stage including numerous wasps and beetle larvae.

Dry Decay

Stage 5

Time Frame: 50-365 days after death

The body is now dry and decays very slowly. Eventually all the hair disappears leaving the bones only.

Insect Activity Animals which can feed on hair include tineid moths, and micro-organisms like bacteria. Mites, in turn, feed on these micro-organisms.

They remain on the body as long as traces of hair remain, which depends on the amount of hair that covers the particular species. Humans and pigs have relatively little hair and this stage is short for these species.

Embalming

Embalming affects the process, slowing it somewhat, but does not forestall it indefinitely. Embalmers typically pay the greatest attention to the parts of the body seen by mourners, such as the face and hands. The chemicals that are used in embalming will repel most insects, and slow the process of bacterial putrefaction (the embalming fluid acts to "fix" cellular proteins which means that they cannot act as a nutrient source for bacteria and it also kills the bacteria themselves), but will not preserve a corpse indefinitely. In sufficiently dry environments, an embalmed body may end up mummified. Bodies submerged in peat bogs may become naturally "embalmed", arresting decomposition and resulting in a preserved specimen known as a bog body.

The time for the reduction of an embalmed body to be reduced to a skeleton varies greatly. An unembalmed adult body buried six feet deep in ordinary soil without a coffin normally takes ten to twelve years to decompose fully to a skeleton, given a temperate climate. Immerse the body in water, and skeletonization occurs approximately four times faster; expose it to air, and it occurs eight times faster. The skeleton itself is not permanent; acids in soils can reduce it to unrecognisable components as well (this is one reason given for the lack of human remains found in the wreckage of the Titanic, even in parts of the ship considered inaccessible to scavengers). Bodies exposed to cool, damp soil may develop a waxy substance called adipocere, caused by the action of soil chemicals on the body's proteins and fats. The formation of adipocere slows decomposition by inhibiting the bacteria that cause putrefaction.

Importance to forensics

Various sciences study the decomposition of bodies. These sciences fall under the general rubric of forensics, because the usual motive for study of the decomposition of human bodies is to determine the time and cause of death, for legal purposes:

  • Forensic pathology studies the clues to the cause of death found in the corpse as a medical phenomenon
  • Forensic entomology studies the insects and other vermin found in corpses; the sequence in which they appear, the kinds of insects, and where they are found in their life cycle are clues that can shed light on the time of death, the length of a corpse's exposure, and whether the corpse was moved.
  • Forensic anthropology is the branch of physical anthropology that studies skeletons and human remains, usually to seek clues as to the identity, race, and sex of their former owner.

The Body Farm, located at the University of Tennessee in Knoxville has a number of bodies laid out in various situations in a fenced in plot near the medical center. Scientists at the University study how the human body decays in various circumstances to gain a better understanding into decomposition.

Peter Greenaway's film A Zed and Two Noughts [1] has a sub plot which explores decomposition and is intercut with an escalating series of time-lapse sequences watching various plants and animals decomposing, culminating with the decomposition of the two main characters in the film.

Books

Retrieved from "http://en.freepedia.org/Decomposition.html"


Views
Personal tools
In other languages
Similar Links