The goose pimples seen on human skin in the cold are produced by
- A. dilation of the surface capillaries
- B. contraction of the erector pili muscles, which pull the hairs upright
- C. the emptying of the sweat glands
- D. the thickening of the subcutaneous fat layer
Explanation
Each hair has a small erector muscle that pulls it erect, and in a furry mammal this traps a thicker layer of still air as insulation. Human body hair is far too sparse for this to help, so the raised bumps are essentially a vestigial response inherited from hairier ancestors. Subcutaneous fat does insulate, but its thickness cannot change from minute to minute.