How is death medically defined?

Human death is generally recognized by cardiac and respiratory arrest and brain death.

The 1968 Harvard Medical School Ad Hoc Committee defined death as irreversible coma or brain death:

The irreversible and permanent cessation of whole-brain function is called brain death. It includes:

(a) Cessation of brain function: in addition to movement and sensation, the functions of mental activity such as thinking and feeling, i.e., consciousness, are also permanently lost. Brain waves disappear. If the brain stem function still exists, there is spontaneous respiration, can not be called brain death, can only be said to be in a "vegetative state".

(2) cessation of brainstem function: the brainstem has important structures such as reticular formation, nucleus accumbens, medullary vasomotor center and respiratory center. Therefore, loss of brainstem function means cessation of function of the above mentioned structures.

Loss of function of reticular formation leads to coma; loss of function of cerebral nerve causes loss of light reflex, corneal reflex, eye reflex, vestibular reflex, pharyngeal reflex and cough reflex; and loss of function of medulla oblongata leads to cessation of spontaneous respiration and a sharp drop in blood pressure until brain death.

Expanded information:

Phases of death:

1, near-death stage: the main feature is the loss of function or deep inhibition of the nerve centers above the brain stem, which is manifested by Sluggish reaction, blurred consciousness or disappearance. Various reflexes are sluggish or weakened, and respiratory and circulatory functions are progressively weakened.

2. Clinical death stage: the main feature is that the medulla oblongata is in a state of deep inhibition and loss of function, with various reflexes disappearing, cardiac arrest and respiratory arrest. The latter two are considered to be signs of clinical death.

3. Biological death: the final stage of death. In this period, the metabolism of each vital organ stops successively and irreversible metabolism occurs. It is impossible to resurrect the whole organism.

After death, the remains of the organism become part of the biogeochemical cycle. The remains may be eaten by predators or scavengers. Organic matter may be further decomposed by scavenging organisms and then returned to the environment and reused by the food chain. Instead of the species accumulating more and more Earth space becomes smaller and smaller. Scavengers include earthworms, earthworms, dung beetles, and more.

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