These are covered at an angle by two rectangular muscles, "the bedsheet that covers the ice-cream cone", the depressor labii inferioris
, pulling the lower lip down and out, which we use to express irony (Fig 2).
In patients with isolated marginal mandibular nerve weakness, a lack of depressor labii inferioris function can be quite noticeable because an affected patient is unable to evert, depress, or lateralize the lower lip.
Resection of the depressor labii inferioris muscle on the contralateral side can improve facial symmetry at rest and with smiling.
the mandibular lamina (the depressor labii inferioris
, the mentalis, the risorius, the depressor anguli oris, the inferior part of the orbicularis oris, and perhaps the buccinator and the levator anguli otis)