Death

From Wikipedia, the free encyclopedia

Death is the end of the life of a biological organism. Death may refer to the end of life as either an event or condition.^[1] Many factors can cause or contribute to an organism's death, including predation, disease, habitat destruction, senescence, malnutrition and accidents or physical injury. The principal causes of human death in developed countries are diseases related to aging.^[1] Traditions and beliefs related to death are an important part of human culture, and central to many religions. In medicine, biological details and definitions of death have become increasingly complicated as technology advances.

Contents 1 Biology 1.1 Fate of dead organisms 1.2 Competition, natural selection and extinction 1.2.1 Extinction 1.3 Evolution of aging 2 In medicine 2.1 Definition 2.1.1 Misdiagnosed death 2.2 Causes of human death 2.2.1 Signs 2.2.2 Autopsy 2.3 Life extension 2.4 The physician's perspective 3 Death in culture 4 See also 5 References 5.1 Additional references 6 External links

[edit] Biology

[edit] Fate of dead organisms

In animals, small movements of the limbs (for example twitching legs or wings) known as a postmortem spasm can sometimes be observed following death. Pallor mortis is a postmortem paleness which accompanies death due to a lack of capillary circulation throughout the body. Algor mortis describes the predictable decline in body temperature until ambient temperature is reached. Within a few hours of death rigor mortis is observed with a chemical change in the muscles, causing the limbs of the corpse to become stiff (Latin rigor) and difficult to move or manipulate. Assuming mild temperatures, full rigor occurs at about 12 hours, eventually subsiding to relaxation at about 36 hours; however, decomposition is not always a slow process. Fire, for example, is the primary mode of decomposition in most grassland ecosystems.^[2]

Some organisms have hard parts such as shells or bones which may fossilize before decomposition can occur. Fossils are the mineralized or otherwise preserved remains or traces (such as footprints) of animals, plants, and other organisms. Fossils vary in size from microscopic, such as single cells, to gigantic, such as dinosaurs. A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates, or the chitinous exoskeletons of invertebrates. Preservation of soft tissues is extremely rare in the fossil record.

[edit] Competition, natural selection and extinction

Main articles: Competition (biology), natural selection, and extinction

Death is an important part of the process of natural selection. Organisms that are less adapted to their current environment than others are more likely to die having produced fewer offspring, reducing their contribution to the gene pool of succeeding generations. Weaker genes are thus eventually bred out of a population, leading to processes such as speciation and extinction. It should be noted however that reproduction plays an equally important role in determining survival, for example an organism that dies young but leaves many offspring will have a much greater Darwinian fitness than a long-lived organism which leaves only one.

[edit] Extinction

Extinction is the cessation of existence of a species or group of taxa, reducing biodiversity. The moment of extinction is generally considered to be the death of the last individual of that species (although the capacity to breed and recover may have been lost before this point). Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the fossil record) after a period of apparent absence.

Through evolution, new species arise through the process of speciation — where new varieties of organisms arise and thrive when they are able to find and exploit an ecological niche — and species become extinct when they are no longer able to survive in changing conditions or against superior competition. A typical species becomes extinct within 10 million years of its first appearance,^[4] although some species, called living fossils, survive virtually unchanged for hundreds of millions of years. Only one in a thousand species that have existed remain today.^[4][5]

Prior to the dispersion of humans across the earth, extinction generally occurred at a continuous low rate, interspersed with rare mass extinction events.

After death an organism's remains become part of the biogeochemical cycle. Animals may be consumed by a predator or scavenger. Organic material may then be further decomposed by detritivores, organisms which recycle detritus, returning it to the environment for reuse in the food chain. Examples include earthworms, woodlice and dung beetles. Microorganisms also play a vital role, raising the temperature of the decomposing material as they break it down into simpler molecules. Not all material need be decomposed fully however; for example coal is a fossil fuel formed in swamp ecosystems where starting approximately 100,000 years ago, and coinciding with an increase in the numbers and range of humans, species extinctions have increased to a rate unprecedented^[6] since the Cretaceous–Tertiary extinction event. This is known as the Holocene extinction event and is at least the sixth such extinction event. Some experts have estimated that up to half of presently existing species may become extinct by 2100.^[7]

[edit] Evolution of aging

Main article: Evolution of aging

Enquiry into the evolution of aging aims to explain why almost all living things weaken and die with age (N.B. hydra and the possibility of biological immortality). There is not yet agreement in the scientific community on a single answer. The evolutionary origin of senescence remains one of the fundamental puzzles of biology.

[edit] In medicine

[edit] Definition

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 have rendered that definition inadequate because breathing and heartbeat can sometimes be restarted. This is now called "clinical death". Events which were causally linked to death in the past no longer kill in all circumstances; without a functioning heart or lungs, life can sometimes be sustained with a combination of life support devices, organ transplants and artificial pacemakers.

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 must be harvested as quickly as possible after the death of the body.

The possession of brain activity, or ability to resume 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))

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 possible 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 — irreversible 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 sustenance to the front of American politics.

Even by whole-brain criteria, the determination of brain death can be complicated. EEGs can detect spurious electrical impulses, while certain drugs, hypoglycemia, hypoxia, or hypothermia can suppress or even stop brain activity on a temporary basis. Because of this, hospitals have protocols for determining brain death involving EEGs at widely separated intervals under defined conditions.

[edit] Misdiagnosed death

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 Britain became obsessively worried about living after being declared dead.

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.^[8] 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 resuscitation 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). However, some states allow paramedics to pronounce death. This is usually based on specific criteria. Aside from the above mentioned, conditions include advanced measures including CPR, intubation, IV access, and administering medicines without regaining a pulse for at least 20 minutes.

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.^[8] This "diving response", in which metabolic activity and oxygen requirements are minimal, is something humans share with cetaceans called the mammalian diving reflex.^[8]

As medical technologies advance, ideas about when death occurs may have to be re-evaluated in light of the ability to restore a person to vitality after longer periods of apparent death (as happened when CPR and defibrillation showed that cessation of heartbeat is inadequate as a decisive indicator of death). The lack of electrical brain activity may not be enough to consider someone scientifically dead. Therefore, the concept of information theoretical death has been suggested as a better means of defining when true death actually occurs, though the concept has few practical applications outside of the field of cryonics.

There have been some scientific attempts to bring dead organisms back to life, but with limited success.^[9] In science fiction scenarios where such technology is readily available, real death is distinguished from reversible death.

[edit] Causes of human death

See also: List of causes of death by rate

Death can be caused by disease, suffocation/asphyxiation or prolonged lack of oxygen to the brain, or physical trauma as a result of an accident ("unintentional circumstance"), homicide ("intentional act by someone else"), or suicide ("intentional act against one's self").^[10] The leading cause of death in developing countries is infectious disease. The leading causes of death in developed countries are atherosclerosis (heart disease and stroke), cancer, and other diseases related to obesity and aging. These conditions cause loss of homeostasis, leading to cardiac arrest, causing loss of oxygen and nutrient supply, causing irreversible deterioration of the brain and other tissues. With improved medical capability, dying has become a condition to be managed. Home deaths, once the norm, are now rare in the developed world.

In developing nations, inferior sanitary conditions and lack of access to medical technology makes death from infectious diseases more common than in developed countries. One such disease is tuberculosis, a bacterial disease which killed 1.7 million people in 2004.^[11]

Many leading developed world causes of death can be postponed by diet and physical activity, but the accelerating incidence of disease with age still imposes limits on human longevity. The evolutionary cause of aging is, at best, only just beginning to be understood. It has been suggested that direct intervention in the aging process may now be the most effective intervention against major causes of death.^[12]

[edit] Signs

The signs of death, strongly indicating that a person is no longer alive, are:

• Pallor mortis, paleness which happens almost instantaneously (in the 15–120 minutes after the death)
• Algor mortis, the reduction in body temperature following death. This is generally a steady decline until matching ambient temperature
• Rigor mortis, the limbs of the corpse to become stiff (Latin rigor) and difficult to move or manipulate
• Livor mortis, a settling of the blood in the lower (dependent) portion of the body
• Decomposition, the reduction into simpler forms of matter

[edit] Autopsy

Main article: Autopsy

An autopsy, also known as a postmortem examination or an obduction, is a medical procedure that consists of a thorough examination of a human corpse to determine the cause and manner of a person's death and to evaluate any disease or injury that may be present. It is usually performed by a specialized medical doctor called a pathologist.

Autopsies are either performed for legal or medical purposes. A forensic autopsy is carried out when the cause of death may be a criminal matter, while a clinical or academic autopsy is performed to find the medical cause of death and is used in cases of unknown or uncertain death, or for research purposes. Autopsies can be further classified into cases where external examination suffices, and those where the body is dissected and an internal examination is conducted. Permission from next of kin may be required for internal autopsy in some cases. Once an internal autopsy is complete the body is reconstituted by sewing it back together. Autopsy is important in a medical environment and may shed light on mistakes and help improve practices.

A necropsy is a postmortem examination performed on a non-human animal, such as a pet.

[edit] Life extension

Main article: Life extension

Life extension refers to an increase in maximum or average lifespan, especially in humans, by slowing down or reversing the processes of aging. Average lifespan is determined by vulnerability to accidents and age-related afflictions such as cancer or cardiovascular disease. Extension of average lifespan can be achieved by good diet, exercise and avoidance of hazards such as smoking and excessive eating of sugar-containing foods. Maximum lifespan is determined by the rate of aging for a species inherent in its genes. Currently, the only widely recognized method of extending maximum lifespan is calorie restriction. Theoretically, extension of maximum lifespan can be achieved by reducing the rate of aging damage, by periodic replacement of damaged tissues, or by molecular repair or rejuvenation of deteriorated cells and tissues.

Researchers of life extension are a subclass of biogerontologists known as "biomedical gerontologists". They seek to understand the nature of aging and they develop treatments to reverse aging processes or to at least slow them down, for the improvement of health and the maintenance of youthful vigor at every stage of life. Those who take advantage of life extension findings and seek to apply them upon themselves are called "life extensionists" or "longevists". The primary life extension strategy currently is to apply available anti-aging methods in the hope of living long enough to benefit from a complete cure to aging once it is developed, which given the rapidly advancing state of biogenetic and general medical technology, could conceivably occur within the lifetimes of people living today.

Many biomedical gerontologists and life extensionists believe that future breakthroughs in tissue rejuvenation with stem cells, organs replacement (with artificial organs or xenotransplantations) and molecular repair will eliminate all aging and disease as well as allow for complete rejuvenation to a youthful condition. Whether such breakthroughs can occur within the next few decades is impossible to predict. Some life extensionists arrange to be cryonically preserved upon legal death so that they can await the time when future medicine can eliminate disease, rejuvenate them to a lasting youthful condition and repair damage caused by the cryonics process.

[edit] The physician's perspective

A qualitative survey of internal medicine doctors in the United States found three sources of satisfaction from medical practice:^[clarify]

1. realizing a fundamental change in perspective via an experience with a patient
2. making a difference in someone's life
3. connecting with patients

The authors of the survey noted how often the meaningful events, such as connecting with patients, occurred at events, such as death, that normally suggest a failure of medical care.^[13] The following research suggests factors associated with a meaningful death.

A qualitative study using focus groups that consisted of "physicians, nurses, social workers, chaplains, hospice volunteers, patients, and recently bereaved family members". The groups identified the following themes associated with a 'good death'.^[14] The article is freely available and provides much more detail.

1. Pain and Symptom Management. Patients want reassurance that symptoms, such as pain or shortness of breath that may occur at death, will be well treated.
2. Clear Decision Making. According to the study, 'participants stated that fear of pain and inadequate symptom management could be reduced through communication and clear decision making with physicians. Patients felt empowered by participating in treatment decisions'.
3. Preparation for Death. Patients wanted to know what to expect near death and to be able to plan for the events that would follow death.
4. Completion. 'Completion includes not only faith issues but also life review, resolving conflicts, spending time with family and friends, and saying good-bye.'
5. Contributing to Others. A family member noted, "I guess it was really poignant for me when a nurse or new resident came into his room, and the first thing he'd say would be, ‘Take care of your wife’ or ‘Take care of your husband. Spend time with your children.’ He wanted to make sure he imparted that there's a purpose for life."
6. Affirmation of the Whole Person. 'They didn't come in and say, "I'm Doctor so and so." There wasn't any kind of separation or aloofness. They would sit right on his bed, hold his hand, talk about their families, his family, golf, and sports.'
7. Distinctions in Perspectives of a Good Death

A separate study suggests that the patients' preferences will not be stable as death approaches and so the physician should consider re-evaluating these issues.^[15]

In an essay, 'On Saying Goodbye: Acknowledging the End of the Patient–Physician Relationship with Patients Who Are Near Death' suggestions are made to health care providers for saying good-bye to patients near death.^[16] The quotes below are from the article. The article is freely available and provides much more detail.

1. Choose an Appropriate Time and Place
2. Acknowledge the End of Your Routine Contact and the Uncertainty about Future Contact The doctor could say, "You know, I'm not sure if we will see each other again in person, so while we are with each other now I want to say something about our relationship."
3. Invite the Patient To Respond, and Use That Response as a Piece of Data about the Patient's State of Mind The authors suggest saying "Would that be okay?" or "how would you feel about that?"
4. Frame the Goodbye as an Appreciation The authors suggest examples such as "I just wanted to say how much I've enjoyed you and how much I've appreciated your flexibility [or cooperation, good spirits, courage, honesty, directness, collaboration] and your good humor [or your insights, thoughtfulness, love for your family]."
5. Give Space for the Patient to Reciprocate, and Respond Empathically to the Patient's Emotion If the patients becomes tearful, the doctor can provide silence to allow the patient to respond, or the doctor may ask about what the patient is feeling.
6. Articulate an Ongoing Commitment to the Patient's Care Do not make the patient feel abandoned, "Of course you know I remain available to you and that you can still call me".
7. Later, Reflect on Your Work with This Patient

A randomized controlled trial of communication between health care providers and family members at the time of death reported that the intervention decreased the burden of bereavement.^[17] The intervention consisted of a brochure and family conference that focused on the following items that are remembered with the mnemonic value:

• to Value and appreciate what the family members said
• to Acknowledge the family members' emotions
• to Listen
• to ask questions that would allow the caregiver to Understand who the patient was as a person
• to Elicit questions from the family members. Each investigator received a detailed description of the conference procedure

Other difficult issues for physicians include providing sedation for a patient at death and discontinuing life support. The following case reports detail these experiences from the physician's perspective.^[18][19]

[edit] Death in culture

This article should include a summary of death in culture. See Wikipedia:Summary style for information on how to incorporate it into this article's main text.

Main article: Death in culture

[edit] See also

-cide Apocalypse Apoptosis Ars moriendi ("The Art of Dying") Bardo Black Death Coma Danse Macabre Death, Desire and Loss in Western Culture by Jonathan Dollimore Death erection Death metal Death (personification) Death rattle Death Row Death threat Deathbed conversion Día de los Muertos, (Day of the Dead) a holiday Dying declaration Euphemisms for death

Ghost Dance Inheritance Karōshi, (occupational sudden death) List of causes of death by rate Maligno Art Mortician Mot Near-death experience Post Mortem Interval Quantum immortality Reincarnation Reperfusion Shiva Stellar evolution ("death" of a star) Stages of dying Thanatology (death among humans; its causes and social aspects) Undead Yama Zombie

[edit] References

[edit] Additional references

• Pounder, Derrick J. (2005-12-15). POSTMORTEM CHANGES AND TIME OF DEATH. University of Dundee. Retrieved on 2006-12-13.
• Vass AA (2001) Microbiology Today 28: 190-192 at: [1]
• Piepenbrink H (1985) J Archaeolog Sci 13: 417-430
• Piepenbrink H (1989) Applied Geochem 4: 273-280
• Child AM (1995) J Archaeolog Sci 22: 165-174
• Hedges REM & Millard AR (1995) J Archaeolog Sci 22: 155-164
• Cook, C (2006). Death in Ancient China: The Tale of One Man's Journey. Brill Publishers. ISBN 9004153128. 
• Maloney, George, A., S.J. (1980) The Everlasting Now: Meditations on the mysteries of life and death as they touch us in our daily lives. ISBN 0877932018

[edit] External links

• Death at the Open Directory Project
• Death (Stanford Encyclopedia of Philosophy)
• Doctors Change the Way They Think About Death
• Odds of dying from various injuries or accidents Source: National Safety Council, United States, 2001
• Causes of Death
• Causes of Death 1916 How the medical profession categorized causes of death a century ago.
• George Wald: The Origin of Death A biologist explains life and death in different kinds of organisms in relation to evolution.

v • d • e Death and related topics
In medicine	Autopsy · Brain death · Clinical death · Euthanasia · Persistent vegetative state · Terminal illness
Lists	Causes of death by rate · People by cause of death · Notable deaths in 2008 · 2007
Mortality	Immortality · Infant mortality · Legal death · Maternal death · Mortality rate
After death	Afterlife · Burial · Cremation · Decomposition · Funeral · Grief · Mourning · Promession · Resomation · Séance · Customs
Fields of research	Cryonics · Near-death experience · Near-death studies · Reincarnation research
Other	Genocide  · Fascination with death · Martyrdom · Sacrifices (Human · Animal) · Suicide · War · Personification of Death  · Death and culture