Depressor labii inferioris
Depressor labii inferioris
- Latin synonym: Musculus depressor labii inferioris
- Synonym: Depressor labii inferioris muscle; Quadratus labii inferioris muscle
Definition
Depressor labii inferioris | |
Origin | Oblique line of mandible below the mental foramen |
Insertion | Skin of lower lip, blends with orbicularis oris fibres |
Blood supply | Facial and maxillary arteries |
Innervation | Facial nerve |
Action | Depresses and everts the lower lip |
The depressor labii inferioris is a muscle of facial expression located in the lower lip region. Its primary function is to depress and evert the lower lip.
Anatomical details
1. Origin
The depressor labii inferioris muscle arises from the oblique line of the mandible, below the mental foramen, between the foramen and the symphysis menti. At its origin, it is continuous with the fibres of the platysma, and laterally, it is partially covered by the depressor anguli oris muscle.
2. Insertion
The muscle fibres pass upward and medially to insert into the skin of the lower lip. Some fibres interdigitate with fibres of the contralateral muscle in the midline, while others blend with the concentric fibres of the orbicularis oris.
Blood supply
Inferior labial branch of the facial artery
Mental branch of the maxillary artery
Innervation
Marginal mandibular branch of the facial nerve (cranial nerve VII).
Actions
Depresses and everts the lower lip.
Acts synergistically with the platysma and depressor anguli oris to lower the lower lip to produce expressions of sadness and doubt.
References
Gray, H. (2016) Gray’s Anatomy: The Anatomical Basis of Clinical Practice. 41st edn. Edited by S. Standring. New York: Elsevier. Chapter 30: Face and Scalp, pp. 495.
