What happen after death ? -pathology physiology forensic-
BCSO-What happens after death?
Everybody will die, that is one thing that we are absolutely certain of. What exactly is death, and what happens in the time after death? From a biological point of view, death is a process, not an event. This is because the different tissues and organs in a living body dies at different rates. We can divide death into somatic death and cellular death. Somatic death is when the individual is not longer a unit of society, because he is irreversibly unconscious, and unaware of himself and the world.
Cellular death is when the cells quits respiration and metabolism. When all cells are dead, the body is dead. But all cells do not die simultaneously, except perhaps in a nuclear explosion. Even in a victim of a car bomb, where the body becomes fragmented, individual cells will continue to live for a few minutes or longer. Different celltypes can live for different times after cardiac arrest. Nervous cells in the brain are particulary vulnerable to oxygen deprivation and will die within 3-7 minutes after complete oxygen deprivation.
In many countries brain stem death is considered legal death, even if the body is kept alive with artificial means. This opens up for organ transplants of heart, liver and lungs, where the donor has to be dead.
What we will discuss in this text, is what happens after cardiac arrest in a body wich is lying dead outdoors (or indoors).
One of the first things that happens after death is that the temperature in the body starts to drop. Before the temperature in the body core drops, a temperature gradient must be established from the outside to the core. After this gradient has become established the body temperature will drop with a theoretically predictably rate. This fact can be used to estimate time of death. Even if one succeeds in predicting when the temperature of the body core was 37 degrees Celsius, one has to remember that the time it takes to form the temperature gradient will vary from individual to individual, and will vary from almost no time, to over two hours.
After the onset of putrefaction (about two days after death) the body temperature will increase again, due to the metabolic activity of the bacteria and other decomposing organisms.
Rigor mortis is a well known phenomenon, and is due to a complex chemical reaction in the body. In the living body muscles can function both aerobic and anaerobic. In the dead body muscle cells can only function anaerobically. When muscle cells work anaerobically the end product is lactic acid. In the living body, lactic acid can be converted back, by means of excessive oxygen uptake after an anaerobic exercise. In the dead body this can not happen, and the breakdown of glycogen in the muscles leads irreversebly to high levels of lactic acid in the muscles. This leads to a complex reaction where actin and myosin fuses to form a gel. This gel is responsible for the stiffness felt in the body. This stiffness will not be over before decomposition begins.
As rigor mortis is due to a chemical reaction, the reaction time is due to temperature and the initial concentrations of lactic acid. High metabolic activity in the time just before death, for example when running, leads to higher levels of lactic acid, and shorter time for the rigor mortis to develop. Higher environmental temperature also leads to a shorter reaction time.
In temperate regions the following rules of thumb can be used in estimating death, but must be used with caution:
|Temperature of body||Stiffness of body||Time since death|
|Warm||Not stiff||Not dead more than three hours|
|Warm||Stiff||Dead between 3 to 8 hours|
|Cold||Stiff||Dead between 8 to 36 hours|
|Cold||Not stiff||Dead in more than 36 hours|
Rigor mortis should never be the only basis for estimating time of death.
After death, a lot of internal organisms in the intestine will become very active. Escherishia coli and others will start multiplying, and the decomposition begins. First the intestine and the blood will be attacked, and when gas formation and other things leads to rupture of the intestine other organs will be attacked.
Organs starts decomposing at different times after death, and may also be used in estimating time of death.
The decomposition of a body can be divided into several stages, even if the duration of each stage will vary a lot:
|Initial Decay||The cadaver appears fresh externally but is decomposing internally due to the activities of bacteria, protozoa and nematodes present in the animal before death|
|Putrefaction||The cadaver is swollen by gas produces internally, accompanied by odour of decaying flesh|
|Black putrefaction||Flesh of creamy consistence with exposed parts black. Body collapses as gases escapes. Odour of decay very strong|
|Butyric fermentation||Cadaver drying out. Some flesh remains at first, and cheesy odour develops. Ventral surface mouldy from fermentation|
|Dry decay||Cadaver almost dry; slow rate of decay|