The mentalis muscle, also known as the mentalis muscle of the chin or mentalis muscle of the lower lip, is a small, triangular muscle located in the lower half of the face. It is part of the muscular system of the face, which is responsible for controlling facial expressions and movements.
Structure
The mentalis muscle is a small, triangular muscle located in the lower half of the face. It originates from the mental protuberance, a bony protuberance located on the mandible (lower jaw bone). The muscle has a thin, pointed shape and is composed of a single belly and two heads. The muscle fibers of the mentalis muscle run in a vertical direction, from the origin at the mental protuberance to the insertion at the skin of the lower lip.
Location
The mentalis muscle is located in the lower half of the face, just below the lower lip. It is situated in close proximity to other muscles of the face, including the orbicularis oris (muscle of the mouth), the risorius (muscle of the cheek), and the buccinator (muscle of the cheek).
Function
The primary function of the mentalis muscle is to elevate the lower lip and protrude the chin. This action is responsible for producing the pouting or pursing of the lips, which is often associated with expressions of anger or determination. The mentalis muscle also plays a role in the movement of the lower lip during speech and the formation of facial expressions.
Clinical Significance
Dysfunction or injury to the mentalis muscle can result in abnormalities in facial expression and movement. For example, paralysis or weakness of the mentalis muscle may cause a drooping or sagging of the lower lip, which can affect speech and facial expression. In cases where the mentalis muscle is overactive or hyperactive, excessive protrusion of the chin may occur, leading to a condition known as “chin thrust.”
Treatment for abnormalities of the mentalis muscle may involve physical therapy, injections, or surgery, depending on the severity of the condition.
