| Associated with the follicle are sebaceous glands and the arrector pili smooth muscle fiber bundle. |
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| The glands discharge their contents by the contraction of the arrector pili muscle and by any pressure applied to the gland. |
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| Associated with the hair follicle are nerve endings and a muscle, the arrector pili. |
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| At the hair follicle, one or several sebaceous glands and an arrector pili muscle, which causes the hair to stand on end, can be found. |
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| When these structures were placed into the recipient area, the hair unit, including arrector pili muscle and neural connections, also developed. |
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| In fact, the arrector pili muscle and the sebaceous glands are missing. |
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| They also lack arrector pili, so their fur can be streamlined as they swim. |
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| A small muscle, the arrector pili, is attached to each hair follicle, with the exception of the small follicles that produce only fine vellus hairs. |
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| The structure consisting of hair, hair follicle, arrector pili muscles, and sebaceous gland is an epidermal invagination known as a pilosebaceous unit. |
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