Depressor Labii Inferioris is a facial muscle that is located under the lips, at the chin. Â It is also known as the quadratus labii inferioris and the quadratus menti.
Depressor Labii Inferioris
Structure
The depressor labii inferioris muscle is a quadrangular facial muscle which is found within the jaw area that pulls the lower lip downwards as well as laterally that helps in creating facial expression.
Origin
The depressor labii inferioris originates via anterior of the mandible, deep towards the depressor anguli oris.
Insertion
The fibers travel superiorly and medially, some combine together with fibers via the same muscle on the corresponding part as well as fibers via the orbicularis oris prior to its insertion within the lower lip.
It extends the fibers of the platysma muscle while its own fibers are combined with yellow fat.
Relations
It is reinforced by the other muscles that depress the lip:
- Risorius
- Depressor anguli oris
Nerve Supply
The mandibular division of the facial nerve supplies the depressor labii inferioris.
Action
- It draws lower lip downwards and laterally and displays lower teeth.
- It helps in order to create facial expressions.
- It helps in activities like trumpet/saxophone playing and kissing.
Clinical Significance
Generally, the diseases involving the depressor labii inferioris consist of:
- Myalga
- Stroke
- Myopathy
- Strains
- Bell’s palsy
- Lacerations
- Contusions
- Infectious myositis
- Tears
- Atrophy
- Neuromuscular diseases
Common signs related to these ailments consist of:
- Lessened movement of the lip.
- Loss of muscle control.
- Muscle spasms.
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