Muscle · Head

Depressor anguli oris

Musculus depressor anguli oris

A flat triangle on the front of the chin, broad below along the jawline and narrowing upward to a point at the corner of the mouth. Pulling on it drags the corner of the mouth down and out — the expression of sadness, and the reason its older name is simply the triangular muscle. At its upper end its fibres do not stop but merge into a dense fibrous knot at the corner of the lips where eight or nine facial muscles meet, so it is continuous with the muscle that lifts the same corner. That shared knot, not bone, is what the muscles of the mouth actually pull against.