: After we die, do our immune system and every cell inside our body die alongwith us or do they just stay there roaming inside us until we get decomposed?
In: 1180
Most of the cells in your body require oxygen delivery from your heart, so once your heart stops beating they won’t last long.
There are, however, lots of bacteria in your digestive system. They’re not technically human, but they do make up part of your body, and those can survive for a very long time after you’ve died.
They die one at a time when they run out of nutrients that sustain them. Some cells take longer than others. Fingernails keep growing after you’re dead.
Not everything dies at once. That’s why organ donation works. The organs are still alive and can be used in another person if taken care of and quickly transplanted. Once we die, or bodies stop breathing and eating, so each individual cell will eventually die shortly after the body dies, but it varies greatly.
“After we die” is a bit ambiguous. There are different ideas of when we are actually dead: maybe the heart stopped, maybe the brain stops normal brain stuff…
However, when we die the body shuts down in stages. Maybe the brain stops sending signals, then we stop breathing, and then heart stops. It’s not instant, and obviously not every cell in the body gets the message immediately. Cells are individual living things, after all, that work together to make a person. They keep chugging along doing there thing until they’ve run out of food and oxygen and can’t do it any more.
When the heart stops, blood stops pumping around. The blood carries oxygen and food to cells, and washes away waste from cells. Your bone marrow will keep making immune cells and antibodies for a bit, but without the blood moving about, they just sit there in the marrow or stranded where they were wen the blood stopped moving. An immune cell in contact with a virus might still eat it, but it’s not going to be washing about bumping into them (and viruses don’t move on their own).
Cells like nerve cells use gobs of energy and will burn through supply of oxygen and sugar really quick, so they’ll run out and die pretty quick. Stuff like skin cells will take longer. The cells that make hair and nails can live for a few days before they start to die off. Muscle cells tighten as they die and tighten some before they release, so deal people become rigid a few hours after death, and can even move.
Relaxation of the muscles that hold our bladders and bowels closed can cause the deceased to pee and poo.
In the gut, the cells lining the gut die of fairly quickly, and the bacteria there start eating away. They produce gases that bloat the abdomen over the next few days, and some can be expelled os posthumous farts. As bacteria begin to break down the lungs, gases expelled can sometimes be heard as moans and groans. The pressure from those processes also force fluids outward and the skin begins to separate in layers (after a few days).
Refrigerating the dead slows pretty much all of these processes, and the embalming done by funeral homes also stops them.
Some are very energy hungry like your brain and heart and die within minutes.
Others have less demand and more food storage and can persist for hours, or even longer if it’s cold.
Once your heart stops all the oxygen and nutrition supply to the other cells stops too so they can only live off whatever they’ve kept stored.
Most of your cells don’t store much and have no way to get more, and so can’t survive on their own for very long.