Dominic Stone
Lips are one of the most prominent and expressive features of the human face. They are soft, movable, and flexible, and help us to eat, speak, and kiss. Lips have muscles, with the main one being the orbicularis oris muscle, which is a complex, multi-layered muscle that surrounds the mouth and extends from the base of the nose to the top of the chin. It is responsible for various movements of the orofacial region and also contributes to the contour of the lip region. The orbicularis oris muscle works in conjunction with other muscles such as the buccinator and pharyngeal constrictor to form the 'buccinator mechanism', which is essential for functions like swallowing, sucking, whistling, chewing, and kissing.
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What You'll Learn
- The main muscle of the lips is the orbicularis oris
- Lips are divided into the upper (labium superioris) and lower lip (labium inferioris)
- The buccinator and orbicularis oris form a functional unit called the 'buccinator mechanism'
- The lips receive their primary blood supply from the inferior and superior labial arteries
- The lips are one of the face's most prominent and expressive features
The main muscle of the lips is the orbicularis oris
Lips are one of the face's most prominent and expressive features. They help us to eat, speak, kiss, and be intimate. The main muscle of the lips is the orbicularis oris, which is a complex, multi-layered muscle that encircles the mouth. It is composed of four independent quadrants that interlace and give only an appearance of circularity. The orbicularis oris is not a simple sphincter muscle like the orbicularis oculi. Instead, it consists of numerous strata of muscular fibres surrounding the mouth, but having different directions.
The orbicularis oris muscle is made up of two parts: a larger peripheral part and a smaller marginal part. The peripheral portion, also called the extrinsic portion, originates from the modiolus and arises from the fibres of the five buccolabial muscles that attach to it. These are the levator anguli oris, depressor anguli oris, buccinator, risorius, and zygomaticus major muscles. 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 to form the vermilion border of the lips at the junction between the skin and mucous membrane.
The orbicularis oris works in conjunction with other muscles and facial features to perform its functions. For example, it works with the buccinator and pharyngeal constrictor to form the "buccinator mechanism", which is important for orofacial functions such as swallowing, sucking, whistling, chewing, vowel pronunciation, and kissing. The buccinator starts at the mandible (jawbone) and moves deeper than the rest of the facial muscles to connect to the modiolus and the upper and lower lips. The modioli, or dense fibromuscular nodules at the angle of the mouth, act as anchors for many facial muscles. These muscles are held together by fibrous tissue and are crucial for facial expression.
The tone of the orbicularis oris depends on the support it receives from the labial flange in the labial vestibule and the position of the teeth. When the mouth is open wide, the muscle becomes stretched, narrowing the sulcus. If the teeth are positioned too far labially, the orbicularis oris can become overstretched. The proper orientation of this muscle is critical, especially in the case of cleft lip reconstruction surgery, where restoring the normal course of the muscle is imperative for its function.
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Lips are divided into the upper (labium superioris) and lower lip (labium inferioris)
Lips are made up of a complex of muscles called the orbicularis oris muscle. This muscle is not a simple sphincter muscle, but a multi-layered muscle with four independent quadrants that interlace. The orbicularis oris muscle is the main muscle of the lips and encircles the mouth. It is attached to the dermis of the upper (labium superioris) and lower lip (labium inferioris).
The superior labial branches, or labial branches, are the largest and most numerous. They descend behind the quadratus labii superioris and are distributed to the skin of the upper lip, the mucous membrane of the mouth, and the labial glands. The superior labial artery is larger and more egregious than the inferior labial artery. It follows a similar course along the edge of the upper lip, supplying the upper lip and giving off vessels that ascend to the nose.
The orbicularis oris muscle is responsible for various movements of the orofacial region and also contributes to the contour of the lip region. It is one of the muscles used in playing all brass instruments and some woodwinds. This muscle closes the mouth and puckers the lips when contracted. It is also part of the "buccinator mechanism", which is important for orofacial functions such as swallowing, sucking, whistling, chewing, vowel pronunciation, and kissing.
Tension on this muscle can result in smoker's lines or vertical lip lines on both the upper and lower lips. In cleft lip cases, the proper orientation of this muscle is crucial for its normal function. During reconstruction surgery, restoring the normal course of the orbicularis oris muscle in the upper lip is imperative.
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The buccinator and orbicularis oris form a functional unit called the 'buccinator mechanism'
The lips are one of the most prominent and expressive features of the human face. They are soft, movable, and very flexible, helping us to communicate our emotions visually. Lips have many functions, including helping us eat, speak, kiss, and be intimate.
The orbicularis oris muscle is the main muscle of the lips. It is a complex, multi-layered muscle that encircles the mouth. It is composed of four independent quadrants that interlace and give only the appearance of circularity. The muscle fibres of the orbicularis oris have origins in other facial muscles that end and join with the lips' own muscle fibres.
The buccinator muscle, on the other hand, is the main muscle of the cheek. It is a thin, quadrilateral facial muscle that provides the cheek with structure and tightness. The buccinator muscle starts at the mandible (jawbone) and moves deeper than the rest of the facial muscles to connect to the modiolus and the upper and lower lips. The buccinator works with the orbicularis oris, stretching the circular fibres around the mouth's cavity.
The buccinator and orbicularis oris form a functional unit called the buccinator mechanism. This mechanism is essential for orofacial functions such as swallowing, sucking, whistling, chewing, and vowel pronunciation. The buccinator mechanism is also important for facial expressions and emotional communication. If the buccinator and orbicularis oris muscles are weakened or paralysed, food may accumulate in the oral vestibule during chewing.
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The lips receive their primary blood supply from the inferior and superior labial arteries
The lips are a facial feature that helps express emotions, eat, speak, and be intimate. They are soft, movable, and flexible, with the lower lip being fuller and larger than the upper lip in most cases. The lips receive their primary blood supply from the inferior and superior labial arteries, which arise from the facial artery at the modiolus.
The facial artery ascends deep to several muscles, including the risorius, zygomaticus major, and zygomaticus minor, and superficial to the buccinator and levator anguli oris. The facial artery then branches into the inferior and superior labial arteries, which supply the upper and lower lips, respectively. The superior labial artery typically branches off from the facial artery about 1.1 cm laterally and 0.9 cm superior to the oral commissure. It has an average external diameter of around 1.6 mm at its origin, with a range of 0.6-2.8 mm.
The superior labial artery provides blood to the upper lip, nasal septum, and ala of the nose, and also contributes to the columellar branches. It forms connections with other vessels and branches, such as the contralateral vessels and the internal carotid system's dorsal nasal artery. On the other hand, the inferior labial artery branches off from the facial artery at a more lateral and inferior position to the oral commissure. It has an external diameter ranging from 0.5 mm to 1.5 mm at its origin.
The inferior labial artery supplies blood to the lower lip by running beneath the depressor anguli oris (triangularis) muscle and piercing the orbicularis oris muscle. It anastomoses, or forms connections, with its counterpart on the opposite side and other arteries, such as the mental branch of the inferior alveolar artery. The facial artery, which gives rise to the labial arteries, continues cranially along the nasolabial fold, becoming the angular artery and branching into the nasal region.
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The lips are one of the face's most prominent and expressive features
The main muscle of the mouth is the orbicularis oris, which is a complex, multi-layered muscle that attaches to the dermis of the upper and lower lips. It is a circle of muscle that surrounds the mouth and consists of four independent quadrants that interlace and give only the appearance of circularity. The orbicularis oris is not a simple sphincter muscle, as it was once thought to be. Instead, it is composed of numerous strata of muscular fibres surrounding the mouth, with different directions and origins in other facial muscles. The buccinator muscle works with the orbicularis oris, stretching the circular fibres around the mouth's cavity. The masseter is another important muscle that controls the opening and closing of the mouth, as well as the pushing out of the chin.
The lips receive their primary blood supply from the inferior and superior labial arteries, which branch from the facial artery. The superior labial artery supplies the upper lip, while the inferior labial artery supplies the lower lip. The facial and labial arteries communicate with the subdermal plexus through a dense population of musculocutaneous perforators. The mental nerve also supplies the lower lip skin down to the labiomental fold and, occasionally, down the chin as well. Proprioceptive fibres associated with mechanoreceptors, such as Merkel cells and Meissner's corpuscles, are present in both lips, contributing to the fine tactile sensitivity essential for speech and oral function.
The lips are essential for facial expressions and, as such, play a crucial role in communication. They are also important for other functions, such as eating and kissing. Understanding the way the muscles of the mouth express emotion is crucial in determining how to depict that emotion in art or drawing. The unique turns, tucks, folds, and roundness of the mouth and lips can be challenging to capture, but the time and patience are well worth it. With careful attention to detail, artists can infuse their subjects with emotive strength.
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Frequently asked questions
Yes, the lips have muscles. The main muscle of the mouth is the orbicularis oris, which is a complex, multi-layered muscle that attaches to the dermis of the upper and lower lips. It is responsible for various movements of the orofacial region and also contributes to the contour of the lip region.
The orbicularis oris muscle is a circle of muscle around the mouth that closes or purses the lips. It is also one of the muscles used in playing brass and some woodwind instruments.
The buccinator, which works with the orbicularis oris, is another important muscle for the lips. It stretches the circular fibres around the mouth's cavity and is used when compressing the lips and cheeks against the teeth. The masseter, which controls the opening and closing of the mouth, is also important.
