How does human skin regulate body temperature on a cold day?

Here's how the human skin regulates body temperature on a cold day:

• Vasoconstriction: Blood vessels in the skin constrict, reducing blood flow to the surface. This minimizes heat loss from the blood to the colder external environment.
• Piloerection: Tiny muscles attached to hair follicles contract, causing hairs to stand upright (goosebumps). This traps a layer of air close to the skin, which acts as an insulating layer to reduce heat loss.
• Reduced sweating: Sweat glands become less active, decreasing the production of sweat. This prevents heat loss through evaporation from the skin's surface.
• Subcutaneous fat: The layer of fat beneath the skin acts as an insulator, further reducing heat loss from the body to the surroundings.