Science Behind Human Body’s Decomposition

Science Behind Human Body's Decomposition Forensic Yard (9)

It is defined as the disintegration of body tissues after death. It is classified under the late changes after death and is a normal fate of a body. However, under certain specific environmental conditions, modified decomposition happens where instead of the body getting completely degraded, it gets preserved for a considerable time. Such modified decomposition may occur in the form of mummification or adipocere formation.  

Decomposition happens when the biochemical process that develops, maintains and preserves the integrity of cellular elements stops. The stages of decomposition are categorized into early and advanced decomposition followed by partial and complete skeletonization.

The components of the tissue leaks and breaks up during decomposition and release hydrolytic enzymes. The complex organ tissues are broken down into simpler compounds. The bacteria and other microorganisms feed on the decomposing body.  

Two parallel processes of decomposition that proceed simultaneously are autolysis and putrefaction. This is followed by skeletonization which will either dissolute completely or form a fossil. Various external and internal factors affect the process of decomposition. These stages are followed unless the body is frozen or cremated.

Process of Decomposition

Autolysis

It is a self-destruction process of the body tissues due to the enzymes released. It occurs on a large scale and does not involve any inflammatory reaction. This process is stimulated when the oxygen level decreases in the body followed by a decrease in intracellular pH.

As it releases hydrolytic enzymes, autolysis happens rapidly in organs like the pancreas, gastric mucosa more rapidly followed by the heart, liver, and kidney. It is most delayed in the fibrous tissues of the uterus or skeletal muscles.

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It is a temperature-dependent process. When gross autolysis happens skin slippage, loosened hairs, and nails. When observed microscopically, it is identified by homogenous and eosinophilic cytoplasm with loss of cellular details with cell remains as debris.

The organs will have a doughy consistency and also the intima of large blood vessels appearing stained by postmortem hemolysis. The gastric wall also ruptures. It can be seen in the fundus region and also ruptures can be seen in the lower end of the Oesophagus.  

Putrefaction

Microorganisms like clostridium welchii, B. coli, Staphylococci, Diphtheroids, non-hemolytic Streptococci, etc. are responsible for putrefaction. This process produces gases like hydrogen sulfide, carbon dioxide, mercaptans, methane, ammonia, etc.

These gases cause bloating, disintegration, and shift in lividity, postmortem purging of feces, semen, decomposition fluid, the expulsion of the fetus from the uterus. In males, the gas is forced from the peritoneal cavity down the inguinal canal into the scrotum causing scrotal swelling.

Hydrogen sulfide reacts with hemoglobin to form sulfhemoglobin and when decomposition progresses it imparts a green hue to the body. The main changes observed during putrefaction are the color change, the liberation of gases, and liquefaction of tissues.

The rate at which putrefaction occurs differs in each body based on the moisture content of the tissues. Color changes due to hemolysis of RBC and formation of sulf methemoglobin.

The splitting of proteins and carbohydrates liberates gases which gives out an offensive odor. The gases are collected in the intestine within 12-18 hours in summer and 18-24 hours in winters. As and when the decomposition progresses the organs get converted into thick semi-fluid matter.  

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Decomposition Changes

External signs include the greenish discoloration of the right side of the abdomen over the right cecal area which eventually spreads over the body and also the putrish odor. Multiple blisters are also formed due to the liberation of gases.

The body becomes bloated. Marbling can also be seen. Red coloration of the teeth can be seen due to hemolysis after exudation of hemoglobin derivatives through the dentine tubules. The invasion of insects causes more damage as the maggots release proteolytic enzymes.

The products of decomposition are acids like acetic, palmitic, oxalic, succinic, lactic, aromatic substances like indole/skatole. Amines and amino acids like leucine, tyrosine, putrescine, cadaverine, enzymes like SGOT, LDH, and gases like CO2, SO2, hydrogen sulfide, ammonia.

The decomposition of internal organs depends on the firmness of organs, moisture content of organs, density of organs, quality of blood in organs and so it is first seen in soft tissue, firm tissue, and finally in the hard tissues.

The organs that putrify early are the brain, mucosa of trachea and larynx, stomach and intestine, spleen, and liver and are late in the esophagus, diaphragm, heart, lungs, kidney, urinary bladder, uterus, and prostate.

The brain becomes discolored, softy and pinkish-gray, and pasty. The larynx and trachea turn brownish and then to green. Stomach and intestine show dark red to brown patches, liver becomes flabby and soft in 12-24 hours and appears foamy or honeycombed and appears to be greenish which later changes to coal black. The lungs and the heart gets filled with blisters, adrenal glands appear like a cyst, and the spleen turns steel-gray in color. 

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Factors Affecting the Decomposition Process

  • If death is associated with septicemia, then decomposition happens faster in females than in males.
  • The cause of death also influences the speed of decomposition.
  • In areas where scars are present, the rate of decomposition is retarded.
  • Bodies of children decompose rapidly as they have more moisture content than older people.
  • Manner of burial also influences. It begins early if the bodies are buried in a shallow grave.
  • The presence of air promotes the process of decomposition.
  • The moisture content of the tissues and temperature also plays a significant role in the process of decomposition. Temperature between 21- 43℃ is most favorable and temperature below 0℃ and above 50℃ retards decomposition. 

Conclusion

Decomposition is the most absolute sign of death. It helps in estimating the time since death. But certain factors like bloating of features make person’s identification difficult. Advanced decomposition may obliterate the cause of death.

As it shifts the postmortem lividity, assessing the position of the body also becomes difficult. While estimating the time since death, the factors that can influence the process should also be considered.  

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