Depressor labii inferioris muscle

Last revised by Dr Daniel J Bell on 17 Apr 2022

The depressor labii inferioris muscle, also known as quadratus labii inferioris muscle, is one of the facial muscles.


  • origin: oblique line of the mandible, medial to the mental foramen
  • insertion: 
    • modiolus at the angle of the mouth
    • ascends to medially insert into lower lip
  • innervationfacial nerve
  • action: depresses the lower lip in a mild lateral direction

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