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The lips are formed by a complex, multi-layered muscle known as the orbicularis oris muscle. This muscle is responsible for controlling the movement and shape of the lips, including actions such as puckering, pouting, twisting, and protruding. The orbicularis oris muscle is part of a group of muscles called the buccolabial group, which are responsible for facial expressions around the mouth. In addition to the orbicularis oris muscle, other muscles that contribute to lip movement include the levator labii superioris, zygomaticus major, and risorius muscles.
| Characteristics | Values |
|---|---|
| Common Name | Orbicularis Oris Muscle |
| Alternative Names | Musculus Orbicularis Oris, "Kissing Muscle" |
| Muscle Type | Complex, multi-layered, circular muscle of facial expression |
| Function | Controls the shape and movement of the lips, including closing, protruding, compressing, puckering, twisting, and pulling centrally |
| Blood Supply | Facial artery, specifically the superior and inferior labial branches |
| Peripheral Portion Origin | Modiolus, with fibres from the buccolabial muscles: levator anguli oris, depressor anguli oris, buccinator, risorius, and zygomaticus major |
| Fibre Direction | Numerous strata of muscular fibres surrounding the mouth, with different directions |
| Fibre Composition | Derived from other facial muscles and proper to the lips, with some fibres from the buccinator, caninus, triangularis, quadratus labii superioris, zygomaticus, and quadratus labii inferioris |
| Upper Lip Composition | Two bands, lateral and medial, with the lateral band connecting to the alveolar border of the maxilla and the medial band connecting to the back of the septum of the nose |
| Lower Lip Composition | Two bands, medial and additional fibres, with the medial band corresponding to the depression called the philtrum |
| Associated Conditions | In newborns, absence of the muscle on one side can result in a partial droop; repetitive actions like drinking through a straw, kissing, sun exposure, and history of cold sores can affect tissue breakdown |
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What You'll Learn
The orbicularis oris muscle
Anatomically, the orbicularis oris muscle may be considered a single muscle. However, functionally, it appears to consist of different parts that can act independently or in conjunction with other facial muscles. It is composed of four independent quadrants that interlace, giving the appearance of circularity. These quadrants are made up of numerous strata of muscular fibres surrounding the mouth but running in different directions. Some of these fibres are derived from other facial muscles, such as the buccinator, while others are proper to the lips. The uppermost and lowermost fibres pass across the lips from side to side without decussation.
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Lips and facial expressions
The lips are formed by the orbicularis oris muscle, a complex, multi-layered muscle that encircles the mouth. It is not a simple sphincter muscle, but rather consists of numerous strata of muscular fibres surrounding the mouth, with fibres running in different directions. The orbicularis oris muscle is responsible for pulling the lip tissue centrally, allowing for actions such as eating, drinking, whistling, and kissing. It is also known as the "kissing muscle" because it puckers the lips when it contracts.
The orbicularis oris muscle is part of a large group of muscles of facial expression called the buccolabial group, which also includes the levator anguli oris, levator labii superioris, zygomaticus major, and other muscles. These muscles work together to control the shape and movements of the lips, such as closing, protruding, and compressing the lips. The buccolabial group is essential for speech and producing various facial expressions, such as anger and sadness.
The upper and lower lips are comprised of the orbicularis oris muscle, which is covered externally by skin and internally by mucosa. The junction between the mucous membrane and the cutaneous skin is the vermilion border. The position and movement of the lips are influenced by several mimetic muscles that elevate and depress the lips. These muscles attach to a connective tissue thickening at the oral commissures called the modiolus. Elevators of the upper lip include the levator labii superioris and the levator labii superioris alequae nasi muscle.
The facial muscles are located around facial openings, such as the mouth, eyes, nose, and ears, or they may extend over the skull and neck. They are divided into several groups, including the oral group, which is specifically responsible for movements of the mouth and lips. The risorius muscle, for example, pulls the angles of the mouth laterally and is often active during smiling.
The mentalis muscle is another muscle that plays a role in facial expressions. It has an inferior and superior portion, with the superior portion lying deep to the depressor labii inferioris muscle. The depressor labii inferioris is one of the lower lip depressors, along with the depressor anguli oris and the mentalis muscles. These muscles contribute to various facial expressions by depressing the corner of the mouth and the lower lip.
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Lips and speech
Lips are formed by the orbicularis oris muscle, a complex, multi-layered muscle that surrounds the orifice of the mouth and forms the majority of the lips. It is composed of four independent quadrants that interlace, giving the appearance of circularity. The orbicularis oris muscle is responsible for pulling the lip tissue centrally, allowing for actions such as eating, drinking, whistling, and kissing. It is also involved in producing various facial expressions, such as anger and sadness.
The upper and lower lips are comprised of the sphincteric orbicularis oris muscle, which is covered externally by skin and internally by mucosa. The junction between the mucous membrane and the cutaneous skin is the vermillion border. The orbicularis oris muscle contributes to the form and shape of the lips. Contraction of this muscle closes and protracts the lips. The position and movement of the lips are further manipulated by several mimetic muscles that elevate and depress the lips. These muscles attach to a connective tissue thickening at the oral commissures, known as the modiolus.
The elevators of the upper lip include the levator labii superioris and the levator labii superioris alequae nasi muscle. The levator muscles attach to the lower lip at or near the modiolus to elevate the lips or oral commissure. Various depressors of the lower lip, such as the depressor anguli oris, depressor labii inferioris, and mentalis muscles, attach to the modiolus and the skin of the lip. The risorius muscle, which is responsible for pulling the angles of the mouth laterally, is often active during smiling.
The orbicularis oris muscle is part of a larger group of muscles called the buccolabial group, which includes the levator anguli oris, levator labii superioris, zygomaticus major, and other facial muscles. The function of the buccolabial group is to control the shape and movements of the lips, which are essential for speech and facial expressions. The buccolabial group works in conjunction with the orbicularis oris muscle to facilitate speech and enable us to produce a wide range of sounds and expressions.
In summary, the lips are formed by the orbicularis oris muscle, which is a complex muscle that surrounds the mouth and controls the shape and movement of the lips. The position and movement of the lips are further manipulated by various mimetic muscles that elevate and depress the lips. These muscles, along with the orbicularis oris, are crucial for speech and enable us to articulate a diverse range of sounds and expressions.
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Lips and eating/drinking
The lips are formed by a complex, multi-layered muscle called the orbicularis oris, which is responsible for pulling the lip tissue centrally, allowing for actions such as eating, drinking, whistling, and kissing. This muscle is not a simple sphincter muscle as it was once thought to be, but rather it consists of numerous strata of muscular fibres surrounding the mouth, with fibres running in different directions. The orbicularis oris muscle is part of a large group of muscles of facial expression called the buccolabial group, which also includes the levator anguli oris, levator labii superioris, and zygomaticus major, among others. These muscles work together to control the shape and movements of the lips, such as closing, protruding, and compressing the lips, which facilitates speech and helps produce facial expressions.
The orbicularis oris muscle is covered externally by skin and internally by mucosa, with the junction between the two forming the vermillion border. The upper and lower lips are comprised of this sphincteric muscle, which contributes to the form and shape of the lips. Contraction of the orbicularis oris muscle closes and protracts the lips, while isolated contractions of particular parts of the muscle can result in various movements such as lip pouting, puckering, and twisting. The position and movement of the lips is further influenced by several mimetic muscles that elevate and depress the lips, including elevators like the levator labii superioris and depressors like the depressor labii inferioris.
The peripheral portion of the orbicularis oris muscle, also known as the extrinsic portion, originates from the modiolus and is formed by the fibres of five buccolabial muscles: the levator anguli oris, depressor anguli oris, buccinator, risorius, and zygomaticus major. Upon reaching the modiolus, the uppermost and lowermost fibres pass into the superior and inferior labial areas, respectively, while the middle fibres crisscross, allowing the upper half to pass into the inferior labial area and vice versa. The marginal portion, or intrinsic portion, consists of a single or double band of muscle fibres that stem from the modiolus toward the midline, passing through the connective tissue of the lips. These fibres curl upon themselves, forming the vermilion border of the lips at the junction between the skin and mucous membrane.
The orbicularis oris muscle is a powerful muscle with only a thin layer of fat protecting it, so repetitive actions like drinking through a straw, kissing, or sun exposure can affect the breakdown of this tissue. Additionally, certain habits like smoking or a history of cold sores can also impact the tissue of this muscle. Understanding the anatomy and function of the orbicularis oris muscle is essential for maintaining the health and functionality of the lips during everyday activities such as eating and drinking.
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Lips and kissing
Lips are formed by a group of muscles known as the buccolabial group, which includes the orbicularis oris muscle. This muscle is responsible for the movement and shape of the lips and is involved in various functions such as eating, drinking, whistling, and
The orbicularis oris muscle is composed of four independent quadrants that interlace, giving the appearance of circularity. It consists of numerous strata of muscular fibres surrounding the mouth, with fibres derived from other facial muscles inserted into the lips and fibres proper to the lips. These fibres pass from the under surface of the skin to the mucous membrane, through the thickness of the lip. The upper and lower lips are comprised of the sphincteric orbicularis oris muscle, which is covered externally by skin and internally by mucosa. The junction between the mucous membrane and the skin is known as the vermilion border.
The orbicularis oris muscle works in conjunction with other facial muscles to control the position and movement of the lips. Elevators of the upper lip include the levator labii superioris and the levator labii superioris alequae nasi muscle, which attach to the lower lip at the modiolus to elevate the lips. Various depressors of the lower lip, such as the depressor anguli oris, depressor labii inferioris, and mentalis muscles, attach to the modiolus and skin of the lip to depress or lower the lip. The risorius muscle, which is part of the buccolabial group, pulls the angles of the mouth laterally and is often active during smiling.
The buccolabial group also includes muscles such as the levator anguli oris, zygomaticus major, zygomaticus minor, buccinator, and depressor labii inferioris. These muscles contribute to facial expressions and movements such as lip pouting, puckering, and twisting. The buccinator muscle, in particular, forms a functional unit with the orbicularis oris and pharyngeal constrictor called the "buccinator mechanism," which is crucial for orofacial functions like swallowing, sucking, whistling, chewing, and kissing.
In summary, the lips are formed by a complex group of muscles, primarily the orbicularis oris, which enables a range of functions, including kissing. The interplay between the orbicularis oris and other facial muscles allows for the intricate movements and expressions we associate with the lips, contributing to essential activities such as eating and drinking, as well as social interactions like kissing and smiling.
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Frequently asked questions
The muscle that forms the lips is called the orbicularis oris muscle.
The orbicularis oris muscle controls the movement of the lips, allowing for actions such as eating, drinking, whistling, and kissing. It is also known as the "kissing muscle" as it puckers the lips when contracted.
The orbicularis oris is a complex, multi-layered muscle that surrounds the orifice of the mouth. It is composed of four independent quadrants that interlace, giving the appearance of circularity.
The buccinator mechanism is a functional unit formed by the orbicularis oris muscle, along with the buccinator and pharyngeal constrictor muscles. It plays an important role in orofacial functions such as swallowing, sucking, whistling, chewing, vowel pronunciation, and kissing.
The modiolar muscles that contribute to the orbicularis oris include the levator anguli oris, depressor anguli oris, buccinator, risorius, and zygomaticus major muscles. Most of the fibers that comprise the orbicularis oris originate from the buccinator muscle.
