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Death

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For other uses, see Death (disambiguation).
Death is the full cessation of vital functions in the biological life. This article discusses death in the biological sense of the term, and its place in various cultures.

The process of dying

Cell death

The body of a dead walrus on Punuk Island, in the Bering Sea
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The body of a dead walrus on Punuk Island, in the Bering Sea

Normal cellular function involves the production of free energy required for vital cellular metabolism, the production of enzymatic and structural protein, the maintenance of chemical and osmotic homeostasis of cell, and cell reproduction. During normal functions, cells require oxygen, phosphate, calcium (C, H, N, O, P, S), nutritional substrates, ATP, which is required as a source of free energy, intact cell membranes, and a steady-state activity that requires O2 consumption. Cell death may occur when any of these functions is interrupted.

Physiological changes leading up to death

The basic events leading to death involve the brain ceasing to supply information vital for controlling ventilation, heart rhythm, and/or vasodilation and vasoconstriction; the lungs being unable to supply O2 exchange with the blood stream; and/or the heart and blood vessels being unable to maintain adequate circulation of blood to vital tissues. In the cerebrovascular system, hemorrhage, pump failure, and decreased CO2 leads to decreased PCO2, which further leads to Cheyne-Stokes respiration.

Problems in the central nervous system that may lead to death include infection, blood vessel disruption, malignant tumors, or metabolic changes such as renal failure, hepatic failure, and pancreatic failure. Early signs of decompensation in the central nervous system include sluggish pupils that are non-reactive to stimuli, and that are dilated and fixed (this is also an effect of certain drugs). Confusion and the inability to orient oneself may also be signs of decompensation. Later signs include lethargy, decreased ability to perform simple cognitive functions, and attention only by tactile, auditory, or visual stimuli. The very late signs include stupor or sleep, withdrawal of purposeless involvement to stimuli without wakefulness or arousal, or loss of bowel control. Other general signs include being in a semi-comatose state (movement occurs only with pain), or in a deep coma (unresponsive to all stimuli).

In the respiratory system, problems that may lead to death include the lack of cerebral blood flow, chronic obstructive pulmonary disease (COPD), infections, and cancer metastasis.

Changes after death

After death, the body core temperature cools. Cooling depends on a number of external factors including the environment and clothing. Furthermore, rigor mortis begins prior to decomposition. During this process, the muscles gradually become hard due to decreased ATP and lactic acidosis within muscle fibrils. This usually begins 2-4 hours after death, though the process may begin earlier. After 9-12 hours, or in a warm enough climate, these effects may disappear.

Another post mortem reaction includes livor mortis, which begins at the moment of death. During livor mortis, the body becomes distended and skin colour progressively changes from green to purple and finally to black. The dependent areas of the body undergo this process first due to the pooling of blood, and this is usually seen within 2 hours of death, with the process of livor mortis reaching its maximum at 8-12 hours.

Determining when death actually occurs

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, but the development of CPR and prompt defibrillation posed a challenge, rendering the previous definition inadequate. This earlier definition of death is now called "clinical death", and even after it occurs, breathing and heartbeat may be restarted in some cases. Events which were causally linked to death in the past are now prevented from having an effect; even without a functioning heart and lungs, a person can be sustained with life-support devices. In addition to such extremes, there is a growing number of people who would quickly die if their organ transplants or cardiac pacemakers failed.

Today, where a definition of the moment of death is required, doctors and coroners usually turn to "brain death" or "biological death": people are considered dead when the electrical activity in their brain ceases (cf. persistent vegetative state). It is presumed that a stoppage of electrical activity indicates the end of consciousness. However, suspension of consciousness must be permanent, and not transient, as occurs during sleep, and especially a coma. In the case of sleep, EEGs can easily tell the difference. Identifying the moment of death is important in cases of transplantation, as organs for transplant (the brain excluded) must be harvested as quickly as possible after the death of the body.

Among human beings, brain activity is a necessary condition to legal personhood in the United States. "It appears that once brain death has been determined … no criminal or civil liability will result from disconnecting the life-support devices." (Dority v. Superior Court of San Bernardino County, 193 Cal.Rptr. 288, 291 (1983))

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. Eventually it is likely that the criterion for death will be the permanent and irreversible loss of cognitive function, as evidenced by the death of the cerebral cortex. All hope of recovering human thought and personality is then gone. However, at present, 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 Determination Of Death Act in the United States). In 2005, the case of Terri Schiavo brought the question of brain death and artificial sustainment to the front of American politics. Generally, in such contested cases the cause of death is anoxia. Oxygen deprivation for about seven minutes is sufficient to kill the cerebral cortex.

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.

There are many anecdotal references to people being declared dead by physicians and then coming back to life, sometimes days later in their own coffin, or when embalming procedures are just about to begin. Owing to significant scientific advancements in the Victorian era, some people in Great Britain became obsessively worried about living after being declared dead. Being buried alive was a particular possibility which concerned many; inventors therefore created methods of alerting the outside world to one's status: these included surface bells and flags connected to the coffin interior by string, and glass partitions in the coffin-lid which could be smashed by a hammer or a system of pulleys (what many failed to realise was that the pulley system would either not work due to the soil outside the coffin, or that the glass would smash in the person's face, covering them in broken glass and earth).

A first responder is not authorized to pronounce a patient dead. Some EMT training manuals specifically state that a person is not to be assumed dead unless there are clear and obvious indications that death has occurred.[[Citing sources citation needed]] These indications include mortal decapitation, rigor mortis (rigidity of the body), livor mortis (blood pooling in the part of the body at lowest elevation), decomposition, incineration, or other bodily damage that is clearly inconsistent with life. If there is any possibility of life and in the absence of a do not resuscitate (DNR) order, emergency workers are instructed to 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 (DOA).

In cases of electrocution, CPR for an hour or longer can allow stunned nerves to recover, allowing an apparently-dead person to survive. People found unconscious under icy water may survive if their faces are kept continuously cold until they arrive at an emergency room.[[Citing sources citation needed]] This "diving response", in which metabolic activity and oxygen requirements are minimal, is something we share with cetaceans (whales, dolphins, etc). [[Citing sources citation needed]]

Signs of approaching death

When death is imminent

Physical death is a progressive process, during which there are some signs that usually indicate that death is imminent. Not all of the following changes occur, nor do they necessarily occur in any particular order, as the body shuts down during the dying process. In general, the following information may help anticipate and understand changes that appear as an individual approaches death and is “actively dying.”

When death occurs

Leading causes of human death

General

:See big killer and List of causes of death by rate.

Developing countries vs. developed countries

According to World Health Organization report for calendar year 2001. [1]

Causes of death in developing countries Number of deaths Causes of death in developed countries Number of deaths
HIV-AIDS 2,678,000 Ischaemic heart disease 3,512,000
Lower respiratory infections 2,643,000 Cerebrovascular disease 3,346,000
Ischaemic heart disease 2,484,000 Chronic obstructive pulmonary disease 1,829,000
Diarrhoeal diseases 1,793,000 Lower respiratory infections 1,180,000
Cerebrovascular disease 1,381,000 Trachea/bronchus/lung cancers 938,000
Childhood diseases 1,217,000 Road traffic accidents 669,000
Malaria 1,103,000 Stomach cancer 657,000
Tuberculosis 1,021,000 Hypertensive heart disease 635,000
Chronic obstructive pulmonary disease 748,000 Tuberculosis 571,000
Measles 674,000 Suicide 499,000

Prenatal Death

There are private companies and institutions such as [HopeXchange] and [The Alan Guttmacher Institute] which track death statistics involving embryos and fetuses:

Consciousness after death

Belief in consciousness continuing after death is common and has endured throughout history. Almost every civilization in history has had some belief system relating to life after death. This point of view holds that consciousness is more than simply a function of the brain.

Physiological consequences

Human remains found in scrub, circa 1900-1910.
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Human remains found in scrub, circa 1900-1910.

For the human body, the physiological consequences of death follow a recognized sequence through early changes into bloating, then decay to changes after decay and finally skeletal remains.

Soon after death (15–120 minutes depending on various factors), the body begins to cool (algor mortis), becomes pallid (pallor mortis), and internal sphincter muscles relax, leading to the release of urine, feces, and stomach contents if the body is moved. The blood moves to pool in the lowest parts of the body, livor mortis (dependent lividity), within 30 minutes and then begins to coagulate. The body experiences muscle stiffening (rigor mortis) which peaks at around 12 hours after death and is gone in another 24 (depending on temperature) as enzymes begin to break down the tissues. Within a day, the body starts to show signs of decomposition (decay), both autolytic changes and from 'attacking' organisms—bacteria, fungi, insects, mammalian scavengers, etc. Internally, the body structures begin to collapse, the skin loses integration with the underlying tissues, and bacterial action creates gases which cause bloating and swelling. The rate of decay is enormously variable and depends on numerous factors. Thus, a body may be reduced to skeletal remains in days, though it is possible under certain conditions for remains to stay largely intact for many years.

Settlement of dead bodies

In most cultures, before the onset of significant decay, the body undergoes some type of ritual disposal, usually either cremation or deposition in a tomb. This is often a grave, but may also be a sarcophagus, crypt, sepulchre, or ossuary, a mound or barrow, or a monumental surface structure such as a mausoleum (exemplified by the Taj Mahal) or a pyramid (as exemplified by the Great Pyramid of Giza).

In Tibet, one method of corpse disposal is sky burial, which involves placing the body of the deceased on high ground (a mountain) and leaving it for birds of prey to dispose of. Sometimes this is because in some religious views, birds of prey are carriers of the soul to the heavens, but at other times this simply reflects the fact that when terrain (as in Tibet) makes the ground too hard to dig, there are few trees around to burn and the local religion (Buddhism) believes that the body after death is only an empty shell, there are more practical ways of disposing of a body, such as leaving it for animals to consume.

In certain cultures, efforts are made to retard the decay processes before burial (resulting even in the retardation of decay processes after the burial), as in mummification or embalming. This happens during or after a funeral ceremony. Many funeral customs exist in different cultures. In some fishing or navy communities, the body is sent into the water, in what is known as burial at sea. Several mountain villages have a tradition of hanging the coffin in woods.

A new alternative is ecological burial. This is a sequence of deep-freezing, pulverisation by vibration, freeze-drying, removing metals, and burying the resulting powder, which has 30% of the body mass.

Space burial uses a rocket to launch the cremated remains of a body into orbit. This has been done at least 150 times.

Graves are usually grouped together in a plot of land called a cemetery or graveyard, and burials can be arranged by a funeral home, mortuary, undertaker or by a religious body such as a church or (for some Jews) the community's Burial Society, a charitable or voluntary body charged with these duties. In some places this has created a land-use problem. For example, in Japan all people are cremated after death. About 10% of the arable land in China is taken up by graves.#redirect [[Template:Fact]]

Customs and superstitions

In China, Japan, Korea, and Taiwan the number 4 is often associated to death due to the sound of the Chinese, Japanese, and Korean words for four and death being similar (for example, 사 in Korean is the Sino-Korean number 4 and the word for death, as in 뇌사 (brain death)). For this reason, hospitals and hotels often omit the 4th, 14th, etc. floors, or substitute the number 4 for the letter 'F'.

Personification of death

"All Is Vanity" by C. Allan Gilbert, suggesting an intertwinement between life and death.
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"All Is Vanity" by C. Allan Gilbert, suggesting an intertwinement between life and death.

Death is also a mythological figure who has existed in popular culture since the earliest days of storytelling. The traditional Western image of Death, known as the Grim Reaper—usually resembling a skeleton, wearing black robes and carrying a scythe—is employed on a tarot card and in various television shows and films. Some examples:

References

See also

External links

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