Assertion: heart's muscle | /r/AtLocation | feather or hair shafts
Facets:
Source sentences:
text: Using small smooth muscles (arrector pili in mammals), which are attached to feather or hair shafts; this distorts the surface of the skin making feather/hair shaft stand erect (called goose bumps or pimples) which slows the movement of air across the skin and minimizes heat loss.