When does the body die?

July 7, 2006 10:22 AM

I've got a probably horribly complicated question about death. How long after the brain stops braining does the body actually die?

I'm driving myself insane with the question of when exactly the body dies.

Now, I'm pretty happy that the actual person (or the spirit or the conciousness) dies when brainwave function flatlines. But what about the rest of your body? When do you consider the cells dead?

Imagine that someone gets shot in the head, brain bits everywhere. The brain is going to flatline pretty quickly. But, it's going to be a while until the cells in your hand (for example) stop trying to grab oxygen and nutrients out of your blood.

So, when could you consider the body dead? When the oxygen runs out? When the last cell divides? When delay starts? And how long would this actually take?

Don't you just love these easy questions?

posted by twine42 to science & nature (15 comments total)

wikipedia entry on death
posted by zerokey at 10:34 AM on July 7, 2006

Faster than you think, twine.

The cells can't grab anything from the blood once it's not circulating and had started to draw back from the capillaries and pool in whatever tissues are closest to the ground (lividity, or livor mortis, begins almost immediately). Without the ATP, the glucose, the oxygen etc., cell walls begin to break down and the cells themselves decompose fairly swiftly (a combination of self-digestion through latent enzymes and bacteria infiltration that the cell no longer fights). Bone and skin cells could hang on for several days, but cells that are more energy-hungry, such as brain cells and muscle, will go within hours. The differential rate at which the cells die is one way of determining time since death in bodies discovered soon after death. The retina, for instance, is a very good early-stage indicator.

This is a massive simplification of course. If you want a *lot* of information about the processes on the body after death... feel free to email me.
posted by methylsalicylate at 10:35 AM on July 7, 2006 [1 favorite has favorites]

Read this.
posted by blue_beetle at 10:41 AM on July 7, 2006

In some jurisdictions, brain death legally is death. Or, to quote Law & Order, "When a neurologist says you're dead, you're dead."
posted by oaf at 10:42 AM on July 7, 2006

You may also would like to check this out.
posted by triolus at 11:17 AM on July 7, 2006

I first thought of this article, although it adds more complexity to the part you have assumed away.
posted by Phred182 at 11:22 AM on July 7, 2006

In organ donor cases, sometimes the body is kept alive a long time after brain death (days. weeks?), as a means of storing the organs without damaging them until the transplant operation can begin. This involves pretty serious medical intervention though.
posted by -harlequin- at 11:29 AM on July 7, 2006

Thanks methylsalicylate.

I assume then that bone and muscle cells use oxygen at different rates but, when that oxygen is depleated, they stop working pretty much simultaniously (assuming they're in the same blood pool).

You can guess the next question, I'm sure - any ideas how long that O2 at 100 saturation to depleated is likely to be?

I was kindof hoping there would be some magic number someone could quote (or even pull out of the air) that said that the cells would effectively suffocate within 2-3 minutes depending on how fit the corpse was in it's former incarnation. Probably predicatably, I was wrong.

Oaf - It's not the actual legal dying that was interesting me. It's kind of an extension of that "how long does the brain live after you cut the head off" line of thought. Each cell lives but has no concept of the collective conciousness, so how long does it spend living on borrowed time after you croak.
posted by twine42 at 11:34 AM on July 7, 2006

Keeping people alive on machines I considered cheating for this question, because when the brain stops oxygenation and circulation should stop. But the concept of organ donors does raise a question - how much is the heart kept alive/viable by the ice? Or rather, how long would the heart stay viable without cooling or forced oxygenation?
posted by twine42 at 11:38 AM on July 7, 2006

You would do well to read Sherwin Nuland's excellent book How We Die.
posted by matildaben at 11:47 AM on July 7, 2006

IANAD, my understanding is that brain death does not necessarily end heart and lung functions - it depends on how much is wiped out. The difference between "vegetable" and "brain dead" probably gets pretty gray. On a mechanically related note, not all of your brain is in your head - it's not just nerve bundles but also brain "gray matter" (ie can learn) that extends down your spine and can learn (I tihnk it's mainly used for simple reflexes - brain matter closer to muscles shortens the nerve signal transmission distance, which reduces the time it takes to get a response signal). It wouldn't surprise me if heart/lung functions could survive massive head trauma (brainn death) by simple mechanism of not being directly controlled from the head (though I'm not usre if this is actually the case).
posted by -harlequin- at 11:53 AM on July 7, 2006

Depends on what you define as death. One would expect that metabolism would continue for a long time in some cells.
posted by Ironmouth at 3:16 PM on July 7, 2006

I've been toying with this question philosophically for years.

The thought experiment goes... if I start cutting off pieces of me, there is no intial change in "me" at all until I go below a certain threshold of cell quantiity and type.

I lose a leg, I'm still me. I lose all extremeties, ditto. Continuing on thus, if eventually I can maintain just the head, I may lose my ability to communicate, but not to perceive. Big chunks of brain aren't needed, but at a certain point, I'd have to go below the minimum threshold needed for self-awareness, at whcih point I'd be dead. I may still have many living cells, though.

No single cell has awareness, likely. No one told the hair on the 'dead' gunshot victim that it is on a dead person. All it knows is to continue its life as long as its basic needs are met... an eternity of instants.

Interesting question, though.
posted by FauxScot at 3:20 PM on July 7, 2006

This is a really interesting question, and the answers only serve to raise more questions.

For instance, if cells start to go really quickly as some respondents have said, how is it then that lost limbs and extremeties are frequently pulled out of farm implements or ex-wives' trash cans and sewed back on. Has a sewed-on hand experienced some cell death?

How long is a severed leg still alive before it is officially pronounced dead?
posted by M.C. Lo-Carb! at 3:49 PM on July 7, 2006

M.C.: Yes, a sewed-on hand has experienced some cell death. Probably more than some. I imagine the popularity of this storyline in dramatic fiction and non-fiction has made people think that sewing a severed limb or digit back on is a) common and b) always perfectly successful. It isn't, not by a long way. Consider the recent research that came out comparing the relative success of CPR in real life to the success rates on television drama, consider that reattaching any part of the body is significantly more complex than that, and extrapolate accordingly.
posted by methylsalicylate at 7:39 AM on July 9, 2006