How is heat transported around the body?
The human body uses a few different sources when it looks to increase its internal temperature. The most consistent and reliable form is the heat energy created through friction as muscles rub together during movement. As energy is used in the body, heat energy radiates from muscles and other respirating cells. This heat is then picked up by the blood and transferred around the body.
Most muscle groups are filled with very fine capillaries that web through the tissue. As you move and use up energy, the heat is absorbed into your blood stream and carried around your body to help regulate your temperature. This can be seen whenever your body temperature is too high or too low. If your body temperature drops too low, your skin normally becomes paler. This is due to your blood vessels constricting and diverting most of your blood to your core in order to protect vital organs. You also begin to shiver in an attempt to generate more heat through muscle friction. When you begin to overheat, your blood vessels closest to your skin will expand, giving you a flushed appearance. Dilated vessels will give off more heat towards your skin that is then carried away by evaporating sweat.