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This page deals with death, the cessation of life. For other meanings of death, see death (disambiguation).

Death is a term that can refer to either the termination of life in a living system, or the state of that organism after that event.

Biologically, death can occur to wholes, to parts of wholes, or to both. For example, it is possible for individual cellss and even organss to die, and yet for the organism as a whole to continue to live; many individual cells can live for only a short time, and so most of an organism's cells are continually dying and being replaced by new ones.

Conversely it is also possible for the organism to die and for cells and organs to live and to be used for transplantation. In the latter case, though, the still-living tissues must be removed and transplanted quickly or they too will soon die without the support of their host.

Irreversibility is often cited as a key feature of death. Accordingly by definition it would not be possible to bring an organism back to life; if an organism lives, this implies that it has not died earlier, even if that seemed the case. Nonetheless, many people do not believe that death is always and necessarily irreversible; thus some have a religious belief in bodily or spiritual resurrection, while others have hope for the eventual prospects of cryonics or other technological means of reversing death.

Biologists believe that the function of death is primarily to permit the operation of evolution.

Table of contents
1 Human death: definitions and significance
2 What happens to humans after death?
3 Physiological consequences of human death
4 Personification of death
5 Mortality rate
6 See also
7 Links

Human death: definitions and significance

By far the most important sort of death to human beings is human death. Thinking about human death raises a number of questions.

First, how can we identify the exact moment at which death has occurred? This seems important, because identifying that moment would allow us to put the correct time on death certificates, make sure that the deceased's will is enacted only after the deceased is truly deceased, and in general guide us regarding when to act as one should act toward a living person and when to act as one should toward a dead person. In particular, identifying the moment of death is important in cases of organ transplant, as organs must be harvested as quickly as possible after death.

Historically, attempts to define the exact moment of death have been problematic. Death was once defined as the cessation of heartbeat (cardiac arrest) and of breathing, for example, but the development of CPR and early defibrillation posed a challenge: either the definition of death was incorrect, or techniques had been discovered that really allowed one to reverse death (because, in some cases, breathing and heartbeat can be restarted). Generally, the first option was chosen. (Today this definition of death is known as "clinical death".)

Today, where a definition of the moment of death is required, we usually turn to "brain death" or "biological death": people are considered dead when the electrical activity in their brain ceases. It is presumed that a stoppage of electrical activity indicates the end of consciousness. However, those maintaining that only the neo-cortex of the brain is necessary for consciousness sometimes argue that only electrical activity there should be considered when defining death. In most places the more conservative definition of death (cessation of electrical activity in the whole brain, as opposed to just in the neo-cortex) has been adopted (for example the Uniform Definition of Death Act in the United States).

Even in these cases, the determination of death can be difficult. EEGs can detect spurious electrical impulses when none exists, while there have been cases in which electrical activity in a living brain has been too low for EEGs to detect. Because of this, hospitals often have elaborate protocols for determining death involving EEGs at widely separated intervals.

Because of the difficulties in determining death, under most emergency protocols, a first responder is not authorized to pronounce a patient dead, and if there is any possibility of life and in the absence of a do not resuscitate order, emergency workers must begin rescue and not end it until a patient has been brought to a hospital to be examined by a physician. This frequently leads to situation of a patient being pronounced dead on arrival.

It might also be worthwhile to entertain the possibility that death does not occur at a particular moment, but unfolds as a process over a period of time. Perhaps, in the end, it is not terribly meaningful to speak of "the exact moment of death".

What happens to humans after death?

Second is the question of what, if anything, happens during and after death, especially to humans. Such questions are of long standing, and belief in an afterlife is common and ancient (see underworld). For many, belief in and information about an afterlife is a consolation in connection with the death of a beloved one or the prospect of one's own death. On the other hand, fear of hell or other negative consequences may make death worse. Human contemplation about death is an important motivation for the development of organized religion.

Many anthropologists feel that the careful burials among Homo neanderthalensis, where ornamented bodies were laid in carefully dug, flower-strewn graves, is evidence of early belief in an afterlife.

While there is increasing modern study on the afterlife, acceptance of its existence or its non-existence continues to be a matter of faith.

Physiological consequences of human death

For the human body, the physiological consequences of death include rigor mortis, algor mortis, livor mortis (dependent lividity) and decomposition (decay).

The deceased person is usually either cremated or deposited in a tomb, often a hole in the earth, called a grave. This happens during or after a funeral ceremony. Many other funeral customs exist in different cultures.

Graves are usually grouped together in a plot of land called a "cemetery" or a "graveyard" and are often arranged by a funeral home or undertaker.

Personification of death

Death is also a popular mythological figure who has existed in mythology and popular culture since the earliest days of storytelling. The traditional image of Death, known as the Grim Reaper, is employed in modern Western culture on a tarot card and in various television and film works. A form of this personification is a major character in the Discworld series by Terry Pratchett, although it has been implied that he is merely a local aspect of the archangel Azrael. An unusual personification of Death appears in Neil Gaiman's Sandman graphic novels. Another famous appearance of death is in Ingmar Bergman's the Seventh Seal, in which occurs the famous chess game against Death on the beach.

Mortality rate

The mortality rate is the measure of number of deaths per total number of persons in a given area and time. An example would be 2 deaths per 10,000 people per year.

See also