system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 how do surgeons cut out the chest and there’s almost no blood coming out and when the hearts exposed there’s no blood.
gpt
The inside of the body is not just full of blood like some bag.  Blood is contained in vessels. 

If youre asking how they cut through the skin without the skin bleeding, it is not “really sharp knives” as the other poster said.  That is incorrect.  They use a cauterization tool that burns the skin as they cut so that the capillaries dont bleed.