Role of erector pili muscle?

The erector pili muscle is an integral part of the skin's anatomy, primarily located diagonally from the hair bulb to the skin's surface. It plays a significant role in our physiological response to cold and emotional states, such as fear, through its ability to contract. This contraction causes the well-known phenomenon of 'goosebumps'. Essentially, the muscle's contraction pulls the skin surface down around the hair follicles, which causes the hairs to stand up. This action can trap air between the hairs, providing an insulative effect that helps to warm the body, much like how animals with thick fur stay warm in cold conditions. This mechanism is more effective in those with denser body hair 1.