Piloerection

Erection of the hair of the skin. Piloerection of the hair, for example, on the arm makes it "stand on end." Piloerection starts when a stimulus such as cold or fright causes a discharge from the (involuntary) nervous system that triggers contraction of the little arrectores pilorum muscles. Contraction of these muscles elevates the hair follicles above the rest of the skin so the hair seems to "stands on end." "Piloerection" is made up of "pilo-" from the Latin "pilus" meaning "hair" + "erection," the condition of being stiff or elevated = elevation of the hair. The term "erection" may also be applied to the stiffening and elevation of other parts of the body.

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Erection of hair due to action of arrectores pilorum muscles.

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pi·lo·erec·tion .pī-lō-i-'rek-shən n involuntary erection or bristling of hairs due to a sympathetic reflex usu. triggered by cold, shock, or fright or due to a sympathomimetic agent

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pi·lo·erec·tion (pi″lo-e-rekґshən) horripilation.