Depressor anguli oris muscle

The depressor anguli oris muscle (triangularis muscle) is a facial muscle. It originates from the mandible and inserts into the angle of the mouth. It is associated with frowning, as it depresses the corner of the mouth.

Depressor anguli oris
Scheme showing arrangement of fibers of Orbicularis oris (triangularis labeled at bottom right).
Muscles of the head, face, and neck (labeled as triangularis near chin).
Details
Origintubercle of mandible
Insertionmodiolus of mouth
Arteryfacial artery
Nervemarginal mandibular branch of the facial nerve
Actionsdepresses angle of mouth
Identifiers
LatinMusculus depressor anguli oris
TA98A04.1.03.026
TA22076
FMA46828
Anatomical terms of muscle

Structure

The depressor anguli oris arises from the lateral surface of the mandible.[1] Its fibres then converge. It is inserted by a narrow fasciculus into the angle of the mouth.[1] At its origin, it is continuous with the platysma muscle, and at its insertion with the orbicularis oris muscle and risorius muscle. Some of its fibers are directly continuous with those of the levator anguli oris muscle, and others are occasionally found crossing from the muscle of one side to that of the other; these latter fibers constitute the transverse muscle of the chin.

The depressor anguli oris muscle receives its blood supply from a branch of the facial artery.

Nerve supply

The depressor anguli oris muscle is supplied by the marginal mandibular branch of the facial nerve.[1]

Function

The depressor anguli oris muscle is a muscle of facial expression.[1] It depresses the corner of the mouth, which is associated with frowning.[1]

Clinical significance

Paralysis

Damage to the marginal mandibular branch of the facial nerve may cause paralysis of the depressor anguli oris muscle.[1] This may contribute to an asymmetrical smile.[1] This may be corrected by resecting (cutting and removing) the depressor labii inferioris muscle, which has a more significant impact on smiling.[1]

See also

Additional images
  • Position of depressor anguli oris muscle
  • Mandible, outer surface, side view
  • The arteries of the face and scalp

References

This article incorporates text in the public domain from page 383 of the 20th edition of Gray's Anatomy (1918)

  1. "Depressor labii inferioris resection: an effective treatment for marginal mandibular nerve paralysis". British Journal of Plastic Surgery. 57 (6): 502–510. 2004-09-01. doi:10.1016/j.bjps.2004.04.003. ISSN 0007-1226.
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