Why do the veins in my hands get large and warm only at night time? This has been bothering me for a while. It seems like it only happens after I've been up for about 8-10 hours. My hands also get warm when this happens and the veins on my hands are huge by the time I go to bed. It's been happening every night now and when I wake they are back to normal (actually small and cold).
Blood vessels are designed in such a way that they can change their diameter, there by regulating the blood flow. This is made possible by the vasoactive substances which are released by the cells surrounding the blood vessels. These substances constricts or dilates blood vessels based on the need.
Blood flow in the capillary networks can be controlled by the body using both hormones and nerves (the sympathetic nervous system).
When your body is too hot, more blood is allowed into the capillary networks and so more heat is lost to the air around the body. When this happens, the skin goes pink or red (often called flushing or blushing).
When your body is too cold, blood is not allowed into the capillary networks and so heat is kept in the body and the skin acts as insulation - this makes the skin look very white.
Thread veins of the LEGS occur when the VENULES dilate (get bigger) and become big enough to be visible through the skin.
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