Depressor labii
Muscles of the head, face, and neck.
Details
Originoblique line of the mandible, between the symphysis and the mental foramen
Insertionintegument of the lower lip, Orbicularis oris fibers, its fellow of the opposite side
Nervemarginal mandibular branch of the facial nerve
Actionsdepression of the lower lip
Antagonistorbicularis oris muscle
Identifiers
Latinmusculus depressor labii inferioris
TA98A04.1.03.033
TA22083
FMA46816
Anatomical terms of muscle

The depressor labii inferioris (or quadratus labii inferioris) is a facial muscle. It helps to lower the bottom lip.

Structure

The depressor labii inferioris muscle arises from the lateral surface of the mandible.[1] This is below the mental foramen, and the origin may be around 3 cm wide.[1] It inserts on the skin of the lower lip, blending in with the orbicularis oris muscle around 2 cm wide.[1] At its origin, depressor labii is continuous with the fibers of the platysma muscle. Some yellow fat is intermingled with the fibers.

Nerve supply

The depressor labii inferioris muscle is supplied by the marginal mandibular branch of the facial nerve.[1][2]

Function

The depressor labii inferioris muscle helps to depress and everts the lower lip.[1] It is the most important of the muscles of the lower lip for this function.[1] It is an antagonist of the orbicularis oris muscle.[1] It is needed to expose the mandibular (lower) teeth during smiling.[1]

Clinical significance

Resection

The depressor labii inferioris muscle may be resected (cut and removed) using surgery to correct an asymmetry of the lower lip when smiling.[1] This asymmetry can be caused by paralysis of the marginal mandibular branch of the facial nerve on one side, so the healthy side may be cut to create symmetry.[1] Local anaesthesia may be used, such as by blocking the mental nerve.[1] This operation tends to be successful.[1]

History

The depressor labii inferioris muscle has also (mainly historically) been called the quadratus labii inferioris muscle.[1]

See also

Additional images

References

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

  1. ^ a b c d e f g h i j k l m Hussain, G; Manktelow, R.T; Tomat, L.R (September 2004). "Depressor labii inferioris resection: an effective treatment for marginal mandibular nerve paralysis". British Journal of Plastic Surgery. 57 (6): 502–510. doi:10.1016/j.bjps.2004.04.003. ISSN 0007-1226 – via ScienceDirect.
  2. ^ Tapiwa Mabvuure, Nigel; Pinto-Lopes, Rui; Bolton, Lauren; Tzafetta, Kallirroi (August 2021). "Lower lip depressor reanimation using anterior belly of digastric muscle transfer improves psychological wellbeing in facial palsy patients". British Journal of Oral and Maxillofacial Surgery. doi:10.1016/j.bjoms.2021.07.025. ISSN 0266-4356.
Categories