Musculus quadratus labii inferioris, also known as the quadratus labii inferioris muscle, is a facial muscle located in the lower region of the face. It is a rectangular-shaped muscle that forms part of the musculature of the lower lip.
The term "musculus quadratus labii inferioris" is derived from Latin, where "musculus" means muscle, "quadratus" translates to square or rectangular, "labii" refers to the lip, and "inferioris" indicates its position as being lower. Therefore, this muscle's name describes its rectangular shape and its location in the lower lip.
The musculus quadratus labii inferioris originates from the mandible's oblique line, which is a bony ridge on the lower jaw. From there, it extends vertically downwards and inserts into the orbicularis oris muscle, forming part of the continuous muscular structure around the mouth.
The primary function of the musculus quadratus labii inferioris is to control the movement and position of the lower lip. It plays a role in various actions involving the lower lip, such as pulling the lower lip downward, helping to pout the lips, and contributing to facial expressions like sadness or frowning. Additionally, it works in coordination with other muscles of the mouth and face to perform tasks such as chewing, speaking, and forming various facial expressions.
Overall, musculus quadratus labii inferioris is a muscle responsible for controlling the lower lip's movement and positioning, contributing to various facial expressions and functions.
