What causes bulging vein/ artery in neck with visible pulse? is it a sign i'm too skinny? or a different underlying condition?

Common finding: Many people are thin enough to have easily visible neck veins and arteries. when you are lying down, these vessels are more prominent and the veins often become difficult to see when you are upright. if your vessels are more prominent than normal (a doctor's physical exam is needed), it can be a sign of a more serious vascular condition, but if you are otherwise healthy, that is very unlikely