Logan Steele
The lips are an essential aspect of the human face, playing a critical role in facial expression, speech, sensation, and physical attraction. The orbicularis oris muscle is a composite muscle that forms the majority of the lips. It is a complex circular muscle that surrounds the mouth and is responsible for closing, protruding, and compressing the lips. The muscle is composed of four independent quadrants that interlace, giving the appearance of circularity. It is also one of the muscles used in playing brass and some woodwind instruments.
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What You'll Learn
- The orbicularis oris muscle is the principal muscle of the lips
- Lips are composed of mucosal membrane, vermilion and cutaneous surfaces
- The buccolabial group of muscles control the shape and movement of the lips
- Lips are essential for facial expression, phonation, sensation, mastication, physical attraction and intimacy
- Lips are composed of a surface epidermis, connective tissue and muscle layer
The orbicularis oris muscle is the principal muscle of the lips
The muscle is responsible for closing, protruding, and compressing the lips, as well as puckering them when it contracts. This function is essential for speech and producing various facial expressions, such as anger and sadness. The orbicularis oris also helps in playing brass and some woodwind instruments.
The orbicularis oris is a composite muscle, consisting of two parts: a larger peripheral part and a smaller marginal part. The peripheral portion, also called the extrinsic portion, originates from the modiolus, arising from the fibers of the buccolabial muscles that attach to it. The marginal portion, or intrinsic portion, consists of a single or occasionally double band of muscle fibers.
The proper fibers of the lips are oblique and pass from the under surface of the skin to the mucous membrane through the thickness of the lip. These fibers also connect the muscle with the maxilla and the septum of the nose above, and with the mandible below. The upper and lower lips, or labium superius oris and labium inferius oris, respectively, contain mucosal membrane, vermilion, and cutaneous surfaces.
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Lips are composed of mucosal membrane, vermilion and cutaneous surfaces
The lips are composed of mucosal membrane, vermilion, and cutaneous surfaces. Lips are muscular folds that encircle the opening of the oral cavity, and they contain the orbicularis oris muscle, which is responsible for closing, protruding, and compressing the lips. This muscle is composed of four independent quadrants that interlace, and it is part of a larger group of muscles called the buccolabial group, which also includes the levator anguli oris, zygomaticus major, and buccinator muscles. The buccolabial group controls the shape and movements of the lips, facilitating speech and facial expressions.
The mucosal membrane, or 'wet' part of the lip, is moistened by labial and other glands associated with the oral cavity. It is covered by a mucous membrane overlying the alveolar ridge, where the teeth are situated. The mucosal membrane is full of capillaries that give the lips their characteristic reddish colour. This membrane is continuous with the oral mucosa of the gingivolabial groove.
The vermilion, or 'dry' part of the lip, does not have sweat or labial glands, nor does it have hair follicles. This lack of a protective layer of sweat and body oils means that the lips dry out faster and are more prone to chapping. The skin of the vermilion is very thin, consisting of three to five cellular layers, in contrast to the 16-layer facial skin. The colour of the vermilion ranges from reddish-pink to brown, depending on ethnicity.
The cutaneous surface of the lips is the outer skin, which is covered by hair follicles. This skin is categorised as stratified squamous epithelium, providing protection against friction, microbial invasion, and desiccation. The appearance of the lips varies with facial movement and is influenced by ethnicity. Smiling, crying, pursing, and pouting can all alter the shape of the upper lip.
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The buccolabial group of muscles control the shape and movement of the lips
The human face has about 20 facial muscles, which are responsible for chewing and making facial expressions. The lips are an essential aspect of the human face and play a critical role in facial expression, phonation, sensation, mastication, physical attraction, and intimacy. The upper and lower lips contain mucosal membranes, vermilion, and cutaneous surfaces. The upper lip extends from the nasolabial folds to the inferior margin of the nose, and the lower lip encompasses the region between the lateral commissures and the labiomental crease of the chin. The upper and lower lips intersect at the mouth angle, referred to as the commissure, which is the point at which several muscles involved in lip movement attach.
The other muscles of the buccolabial group include the levator anguli oris, levator labii superioris alaeque nasi, zygomaticus major, zygomaticus minor, risorius, depressor labii inferioris, depressor anguli oris, mentalis, incisivus superior and inferior, and buccinator muscles. The buccal branch of the facial nerve, or cranial nerve VII, provides motor innervation to the orbicularis oris and elevators of the lip and lip angle. The majority of muscles responsible for depression of the lip are supplied via the marginal mandibular branch of the facial nerve.
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Lips are essential for facial expression, phonation, sensation, mastication, physical attraction and intimacy
Lips are an essential aspect of the human face, and they play a critical role in various functions and expressions. One of the primary functions of the lips is facial expression. The large degree of mobility of the lips allows for substantial movements that enable us to express emotions such as happiness, anger, sadness, disgust, surprise, fear, and contempt. For instance, smiling, frowning, and pursed lips can indicate frustration, disapproval, or dishonesty. Lip expressions, often referred to as micro-expressions, can reveal a person's true feelings, even when their words or controlled facial expressions may be saying something different.
Lips are also essential for phonation, which is the process of sound production for speech. They are involved in the creation of bilabial (m, p, b) and labiodental (f, v) consonant sounds, as well as vowel rounding or labialization. The lips are crucial for whistling and playing wind and brass instruments. Additionally, the lips play a vital role in communication for individuals with hearing loss, as lip-reading allows them to understand speech without perceiving sounds.
Furthermore, lips are important for sensation and mastication (chewing). The lips contain touch and pressure receptors, and they work in conjunction with other oral structures like the teeth, tongue, and cheeks to hold food within the mouth and create an airtight seal that prevents liquids from spilling out. Normal mastication involves a series of highly coordinated physiological functions, and the lips are essential for this process.
Lastly, lips play a role in physical attraction and intimacy. Lip colour and size are often associated with sexual attraction, and lip fullness is linked to elevated estrogen levels, indicating female fertility. The lips are also an erogenous zone, and their appearance can enhance physical attraction.
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Lips are composed of a surface epidermis, connective tissue and muscle layer
Lips are composed of a surface epidermis, connective tissue, and muscle layer. They are soft, pliable anatomical structures that form the mouth margins of most vertebrates. The outer skin of the lips contains hair, sweat glands, and sebaceous (oil) glands. The edges of the lips, known as the vermilion border, are covered with reddish skin and are packed with sensitive nerve endings. The reddish skin acts as a transition layer between the hair-bearing tissue on the outside and the mucous membrane on the inside.
The mucous membrane lines the inside of the lips. In newborn infants, the inner surface is thicker, with sebaceous glands and minute projections called papillae. These structural adaptations seem to aid the sucking process. The orbicularis oris muscle, which encircles the mouth, supplies the majority of the substance to each lip. It is a composite muscle that consists of two parts: a larger peripheral part and a smaller marginal part. The border between these two portions corresponds to the margins of the lips that separate them from the surrounding skin.
The orbicularis oris muscle is composed of numerous strata of muscular fibres surrounding the orifice of the mouth. It consists partly of fibres derived from the other facial muscles inserted into the lips and partly of fibres proper to the lips. The proper fibres of the lips are oblique and pass from the under surface of the skin to the mucous membrane, through the thickness of the lip. The fibres curl upon themselves, forming the vermilion border of the lips at the junction between the skin and mucous membrane.
The peripheral portion, also called the extrinsic portion, originates from the modiolus and arises from the fibres of the buccolabial muscles that attach to it. The buccolabial group includes the levator anguli oris, depressor anguli oris, buccinator, risorius, and zygomaticus major muscles. Most of the fibres that comprise the orbicularis oris originate from the buccinator muscle. The middle fibres decussate, so the upper half passes into the inferior labial area, and the lower half into the superior labial area.
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Frequently asked questions
The muscle that surrounds the mouth and forms the lips is called the orbicularis oris muscle.
The orbicularis oris is a composite muscle that consists of two parts: a larger peripheral part and a smaller marginal part. It is a circular muscle that surrounds the orifice of the mouth and forms the majority of the lips.
The orbicularis oris muscle controls the shape and movements of the lips. It closes, protrudes, compresses, and puckers the lips. It is also one of the muscles used in playing brass and some woodwind instruments.
