Stand and let your hands hang next to your sides for a few minutes. Then, look at the backs of your hands. Do you see any bumps on the surface on top of your veins? What might those be, and what are their function?

Given what we know, we can confirm that when you stand and let your hands hang next to your sides for a few minutes, the bumps you see on your veins are the valves that help move blood to the larger veins.

What we know about vein valves.There are valves located throughout the veins in our bodies. Most of these are located in points where smaller venules fuse with the larger veins. Their function is to prevent blood from flowing back into the smaller veins, thus helping with the normal blood flow of the body.

Given that the veins in our bodies are littered with small valves to help the blood return to the heart correctly, we can confirm that these are the small bumps that we can see when letting our hands down for a few mins, as they fill with the blood they try not to let flow back into the smaller veins.

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Not sure what you mean by this question

Answer : romans built laws to manage the pollution which was lead by smoke produced by the factories.

they had the law tat factories that produces smoke cannot be built near residential buildings.

building of proper sewage system was done to ensure that the waste is carried away from the humans so that they do not get diseases from it.

also they built water systems to provide water in those areas which are drought prone.