Depressor labii inferioris muscle
| Depressor labii | |
|---|---|
 Muscles of the head, face, and neck. | |
| Details | |
| Origin | Oblique line of the mandible, between the symphysis and the mental foramen |
| Insertion | Integument of the lower lip, orbicularis oris fibers, its fellow of the opposite side |
| Nerve | Marginal mandibular branch of the facial nerve |
| Actions | Depression of the lower lip |
| Antagonist | Orbicularis oris muscle |
| Identifiers | |
| Latin | musculus depressor labii inferioris |
| TA98 | A04.1.03.033 |
| TA2 | 2083 |
| FMA | 46816 |
| Anatomical terms of muscle | |
The depressor labii inferioris (or quadratus labii inferioris) is a facial muscle. It helps to lower the bottom lip.
Structure
[edit]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
[edit]The depressor labii inferioris muscle is supplied by the marginal mandibular branch of the facial nerve.[1][2]
Function
[edit]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
[edit]Resection
[edit]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
[edit]The depressor labii inferioris muscle has also (mainly historically) been called the quadratus labii inferioris muscle.[1] Note that in the 1918 edition of Gray's Anatomy illustration used here that its abbreviation is "Quad. labii inf." (sic).
See also
[edit]Additional images
[edit]-
Position of depressor labii inferioris muscle (red). -
Mandible. Outer surface. Side view.
References
[edit]
This article incorporates text in the public domain from page 383 of the 20th edition of Gray's Anatomy (1918)
- ^ 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.
- ^ 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.
