Recent comments in /f/askscience

elevenblade t1_j9e0ztx wrote

Reply to when a limb gets amputated, how do they stop the flow of blood? by EnchantedCatto

Surgeon here: You wouldn’t want to connect a major artery to a major vein — that would result in high pressure oxygenated blood pouring rapidly into the vein, raising pressure in the venous system and wasting oxygen. For large blood vessels we tie them off with ligatures (surgical thread, basically) or clip them shut with metal or plastic clips. Bleeding from smaller vessels is handled with cautery, usually electrocautery or sometimes ultrasonic cautery.

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HandleHoliday7107 t1_j9dz9go wrote

Reply to Why does a stem cell recipient not inherit the immune system of the donor? by Kevin4938

Basically, you can think of there being two parts of the immune system that are wiped out before the transplant - the stem cell part, which is the starting material to make the immune system, and the "memory" immune part, which are the cells that "remember" your past infections and vaccines. The person getting the transplant only gets the stem cells, so they don't have any of the "memory" part. Luckily, the new stem cells can re-make the whole immune system, but you need to re-teach the new stem cells (get new vaccines).

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die_kuestenwache t1_j9dyjnb wrote

Reply to How do our brains know where in the body a nerve impulse came from? by kzorlk0

Basically it has formed in such a way as to correctly associate the impulses it receives with the triggers. And yes there are individual stands of nerves that take certain paths. It doesn't always work. Pain that should be associated with some organs ends up feeling like it comes from somewhere else. There is phantom pain from lost limbs. You can even reprogram it to some degree. People can control and sometimes "feel" prosthetics via their chest muscles for instance.

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