As the title mentions, don’t tourniquets just stop the blood completely, or do they direct the blood to where they should go?
Also, how does it work in the case of amputations?
These may be stupid questions…
In: Biology
It isn’t *that* kind of circuit.
Blood goes out into the body through arteries and returns through veins. The blood vessels split up many times becoming smaller and smaller as they extend into the body, splitting blood flow between all parts of the body. Then the blood is collected and returned through veins which gradually merge together into larger vessels.
Blocking blood flow into your arm for example is going to stop blood flowing in and out of that arm, but it is just one of the split paths the blood can flow. It will just continue to flow down and return by the other paths in the rest of the body. It isn’t like one big highway loop.
It’s a circuit with multiple parallel paths, lots of places where outgoing blood is split into Path A and Path B, and then later Path B is split into C and D. If Path C is blocked, blood can still flow in A, B, and D. Anything downstream of C is blocked, which is why your tourniquets are dangerous and should only be applied if you know what you are doing.
Think of it as a rim of a wheel. From the centre(heart) blood goes to organs through the spokes and comes back to the centre through other spokes. If you apply a tourniquet you block some spokes only. The others aren’t affected.
The tourniquets spot blood from passing that point. There are potential problems of tissue that is life and after is not getting enough blood, it can be a problem for reservation of the limb. Skeletal muscles will survive 1 to 1.5 hours with no oxygen. The huge problem is if the leading is from the head because your brain starts to get damaged after around 1 minute with no oxten.
The circulatory system is a double-branching tree. It is a bit like the electrical grid where on a small scale it is usually like that. If you disconnect a house other houses are not affected. If a small transformer station is damaged stuff after is affected but not the rest of the grid. On a large scale, the power grid is a grid. Electrically you could sally that there are lost of parallel not series connections
The blood from arteries via arterioles and capillaries to veins and then back to the heart. The change between arteries to veins is a relative sort distance.
Look at a high-level level view of the circulatory system at https://upload.wikimedia.org/wikipedia/commons/2/29/Circulatory_System_en.svg If you put a tourniquet on the upper arm it is only blood to the rest of the atm that gets blocked not to the rest of the body. You will see that split to smaller arteries and veins usually further down the limb so you do not block very much above the tourniquet
Think of it like closing off a road in the city. Blood (traffic) can’t go that way so it just goes a different way.
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