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Facial expressions are vital to social communication between humans. They are caused by the movement of muscles that connect to the skin and fascia in the face. These muscles move the skin, creating lines and folds and causing the movement of facial features, such as the mouth and eyebrows.
The facial muscles are just under the skin (subcutaneous) muscles that control facial expression. They generally originate from the surface of the skull bone (rarely the fascia), and insert on the skin of the face. When they contract, the skin moves. These muscles also cause wrinkles at right angles to the muscles’ action line. [2]
The risorius muscle is a highly variable muscle of facial expression. It has numerous and very variable origins, and inserts into the angle of the mouth. It receives motor innervation from branches of facial nerve (CN VII). It may be absent or asymmetrical in some people. It pulls the angle of the mouth sidewise, such as during smiling.
The muscles of the face play a prominent role in the expression of emotion, [1] and vary among different individuals, giving rise to additional diversity in expression and facial features. [29] Variations of the risorius, triangularis and zygomaticus muscles. People are also relatively good at determining if a smile is real or fake.
The muscles of facial expression are all specialized members of the panniculus carnosus, which attach to the dermis and so wrinkle or dimple the overlying skin. Functionally, the muscles of facial expression are arranged in groups around the orbits, nose, and mouth. The muscles acting on the lips: Buccinator; Orbicularis oris (a complex of ...
In humans, the frontalis muscle only serves for facial expressions. [3] In the eyebrows, its primary function is to lift them (thus opposing the orbital portion of the orbicularis), especially when looking up. It also acts when a view is too distant or dim. [5] The frontalis muscle also serves to wrinkle the forehead.
The levator labii superioris (pl.: levatores labii superioris, also called quadratus labii superioris, pl.: quadrati labii superioris) is a muscle of the human body used in facial expression. It is a broad sheet, the origin of which extends from the side of the nose to the zygomatic bone. [1]
It is contributed to by at least nine muscles: orbicularis oris, buccinator, levator anguli oris, depressor anguli oris, zygomaticus major, zygomaticus minor, risorius, quadratus labii superioris, quadratus labii inferioris. [1] [2] Its position and movements are important in moving the mouth, facial expression and in prosthetic dentistry. It ...