This is a great question I still do not understand despite having been a Physician for 30 plus years.
The body does indeed have the mechanisms to stop most bleeding, rebuild some new blood supply, cover over damaged skin with almost normal-looking skin. ( amazing Plastic surgery on the face and breasts for example ).
The body attempts to expel poisons and lethal substances before it is killed. ( nausea, vomiting, diarrhea)
The body attempts to put pressure, fluid pressure to expel small stones in tubes. ( Urethral stones, gall stones, oral ductal stones )
The body will use fever to change the conditions of those pesky viruses or bacteria who are trying to invade us.
The body has a partial dive reflex, and can remarkably shut down in severe cold water to the point that the person appears dead and yet if warmed in time will come back to life. ( no one is dead till they are warm and dead )
Just think of this………..
You slice a small piece of your finger off the finger using a sharp knife, say about 1mm off the natural curve. The bleeding stops and a crust and scar forms and we love to pick it off. Under this scar are small islands of normal skin cells growing and kept moist partially protected from dirt and bacteria. Soon these islands grow out to meet each other and to meet the edges of the original cut. Gradually the new skin is completely able to cover the defect made by the knife. With time the new nerves and small vessels grow into the area and the amazing thing to me is that in months' time the nice rounded curve of the original finger is now there. The thick scars are melted away and reduced to the point that most of us cannot tell that part of that finger curve was gone and now exists.
There are problems with every step above that screws this up.
Question. How do the cells of the skin of the new rounded finger know that “ This is what that curve is supposed to look like now? Enough growing and now smoothing to almost the natural curve of the finger. And yet when my finger is cut off at the first joint ( DIP ) the finger cannot grow backbone and flesh and vessels and new skin to rebuild a new finger? Why not? Lizards can grow new tails. Why can’t I grow a new arm or whole finger?
How do these individual cells know that I am part of a lovely curve and enough is enough ??? ( This often fails and we are left with a “ Scar “. But not always. How does the body know what it is supposed to look like? This is the natural curve and beyond that is air. Kind of amazing to me.
Does our body have an electromagnetic form that tells it “ This is how I am supposed to look and that is not how I supposed to look “.
Is this a spiritual body thing or is it all electrical and magnetic?
Maybe some scientist knows but I don’t know the true mechanism of body repair vs covering over the damage.
And in every step of the way doctors see how this process fails a bit. ( proud flesh of a permanent scar for example )
How do the cells of the clear cornea know the exact curve to grow back and heal a cataract removal scar? ( kind of amazing )
We are beautifully and amazingly made but we have limits.
How does the body know? ….. “ This is the US and that is NOT US ?”
How does my body know that I am kissing you and you are kissing me and the two bodies meet cells next to cells and despite some cells of you coming over to me I still can stop kissing you? We each remain individuals as before despite the mixing of fluids and cells. Surely love and mixing of spirits are involved with this. Can you imagine how my cells swim their way up your tubes and egg meets sperm and out of that a new human being is beginning to cell divide and live for another 86 years? Is this all biochemistry? All is electromagnetism? I myself seriously doubt that. Love and bodies and cells and partial ability to heal but not immortal. Why not? Every living cell on earth is divided into every cell type on earth since the beginning. How do I know that “ you are lovely and you are not me?”