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The lips are two fleshy folds that surround the mouth. They are composed of multiple layers, including skin, subcutaneous tissue, muscle, glandular tissue, and mucosa. Lips are easily movable because they have their own muscles and bordering muscles. The principal muscle of the lips is the circumferential orbicularis oris, which functions primarily as a sphincter for the oral aperture.
| Characteristics | Values |
|---|---|
| What are lips? | Lips are two fleshy folds that surround the oral orifice. |
| Lip structure | Lips are composed of multiple layers: skin, subcutaneous tissue, muscle, glandular tissue, and mucosa. |
| Lip movement | The muscles acting on the lips are considered muscles of facial expression. |
| Lip functionality | Lips are used for eating functions, like holding food or getting it into the mouth. Lips also help to keep food between the upper and lower teeth during chewing. |
| Lip blood supply | The facial artery supplies both lips by its superior and inferior labial branches. |
| Lip nerve supply | The buccal and mandibular branches of the facial nerve supply the orbicularis oris muscle. |
| Lip muscle | The principal muscle of the lips is the circumferential orbicularis oris. |
| Lip shape | The upper and lower lips are referred to as the labium superius oris and labium inferius oris, respectively. |
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What You'll Learn
Lips are composed of multiple layers
The lips are composed of multiple layers, with the outer skin containing hair, sweat glands, and sebaceous (oil) glands. The skin of the lip, with three to five cellular layers, is very thin compared to typical face skin, which has up to 16 layers. The edges of the lips are covered with reddish skin, sometimes called the vermilion border, and are abundantly provided with sensitive nerve endings. The reddish skin is a transition layer between the outer, hair-bearing tissue and the inner mucous membrane. The interior surface of the lips is lined with a moist mucous membrane.
The lips contain the orbicularis oris muscle and superior and inferior labial vessels and nerves. The orbicularis oris muscle is a complex of muscles in the lips that encircles the mouth. It is composed of four independent quadrants that interlace and give only an appearance of circularity. The orbicularis oris muscle forms a continuous band of striated muscle fibres that encircle the oral cavity. Histologically, this muscle is composed of striated muscle fibres that are interspersed with connective tissue, allowing for complex and coordinated movements. It plays a critical role in lip movement, enabling functions such as speech, mastication, and facial expressions.
The lips are also served by the buccal branch of the facial nerve, or cranial nerve VII, which 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. The platysma, which is also involved in depression of the lower lip, receives its innervation via the cervical branch of the facial nerve.
The lips are composed of multiple layers, including the epidermis, subcutaneous tissue, orbicularis oris muscle fibres, and mucosa. The orbicularis oris muscle is the principal muscle of the lips and functions primarily as a sphincter for the oral aperture. It bears no direct bony attachments but is appended by the other oral muscles that attach to it.
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Lips are easily movable
The lips are composed of multiple layers, including skin, subcutaneous tissue, muscle, glandular tissue, and mucosa. Lips have their own muscles and bordering muscles, which make them easily movable. The principal muscle of the lips is the circumferential orbicularis oris, which functions primarily as a sphincter for the oral aperture. The orbicularis oris muscle forms a continuous band of striated muscle fibres that encircle the oral cavity.
The upper and lower lips are referred to as the labium superius oris and labium inferius oris, respectively. 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. This is the point at which several muscles involved in lip movement attach.
The orbicularis oris muscle is a complex of muscles in the lips 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, but consists of numerous strata of muscular fibres surrounding the orifice of the mouth, but having different directions. The orbicularis oris muscle is supplied by the superior and inferior labial branches of the facial artery.
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Lips are used for eating functions
Lips are a vital part of the eating process. They are soft, movable, and serve to facilitate the ingestion of food. Lips are used for eating functions such as suckling, gulping, and getting food into the mouth. The lips are also used to hold food and drink inside the mouth and to keep out unwanted objects.
The lips are composed of a surface epidermis (skin), connective tissue, and, in typical mammals, a muscle layer. The outer skin contains hair, sweat glands, and sebaceous (oil) glands. The edges of the lips, or vermilion border, are covered with reddish skin, with the actual term "vermilion" referring to the coloured portion of either the upper or lower lip. The reddish skin is a transition layer between the outer, hair-bearing tissue and the inner mucous membrane. The interior surface of the lips is lined with a moist mucous membrane.
The upper and lower lips are known as the labium superius oris and labium inferius oris, respectively. The upper lip covers the anterior surface of the body of the maxilla, while the lower lip covers the anterior body of the mandible. The upper lip is raised by the levator labii superioris muscle and is connected to the lower lip by the thin lining of the lip itself. The lower lip is lowered by the depressor labii inferioris muscle and bordered inferiorly by the orbicularis oris muscle. The orbicularis oris is the principal muscle of the lips and functions primarily as a sphincter for the oral aperture.
The lips are easily movable because they have their own muscles and bordering muscles. The muscles acting on the lips are considered muscles of facial expression and are derived from the second pharyngeal arch mesoderm. These muscles are part of the panniculus carnosus, which form attachments with the dermis, resulting in dimpling of the overlying skin. The facial nerve, or cranial nerve VII, provides motor innervation to the orbicularis oris and elevators of the lip and lip angle.
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Lips are important for speech
Lips are an important part of the speech apparatus. The lips are easily movable because they have their own muscles and bordering muscles. The principal muscle of the lips is the circumferential orbicularis oris, which encircles the opening of the mouth. The orbicularis oris muscle is responsible for the many variations in the shape and expression of the lips. The lips can be pressed together to produce sounds such as "p" and "b", or rounded to produce the lip-shape for vowels like "oo". The lips can also be brought into contact with the teeth to produce sounds like "f" and "v". Sounds in which the lips are in contact with each other are called bilabial, while those with lip-to-teeth contact are called labiodental. The lips are also essential for creating suction, which is necessary for babies to breastfeed.
The movement of the lips is key to speech perception. When people perceive speech, they closely watch the form and motion of the lips. This is evident from the phenomenon of lip-reading, which is often used by people with hearing loss to understand speech without needing to perceive the actual sounds. The position and movement of the lips can also help distinguish subtle speech differences, such as the articulation of the vowel sound "oo" in English and French. In French, the "oo" sound is produced with more visible lip protrusion and tongue positioning than when making the same sound in English.
The development of lip and jaw coordination for speech goes through three primary phases: integration, differentiation, and refinement. This development begins in infancy and continues to undergo refinement past the age of six. Infants generally produce well-formed jaw movements, but the lips are often compressed by the elevating forces of the jaw during oral closure. As children grow, they master some vocal tract ensembles or speech gestures earlier than others. The formation of these articulatory gestures must operate within the coordinative constraints imposed on individual articulators by the motor system. The lips are also important for creating different sounds, such as labial, bilabial, and labiodental consonant sounds, as well as vowel rounding.
The lips are composed of a surface epidermis (skin), connective tissue, and a muscle layer. The skin of the lip is very thin compared to typical face skin, with only three to five cellular layers. The reddish area within the borders of the lips is called the vermilion zone, and it is abundantly provided with sensitive nerve endings. The interior surface of the lip is lined with a moist mucous membrane.
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Lips are susceptible to diseases
The lips are made up of several different types of tissue, including muscle, but they are also susceptible to a variety of diseases and conditions that can affect their appearance and function. Due to their location and frequent exposure, lips can be vulnerable to various ailments, some unique to this area, and others which are more general but can have specific impacts on the lips.
One of the most common issues affecting the lips is cold sores, caused by the herpes simplex virus (HSV). This highly contagious virus can result in painful blisters that often recur, and while there is no cure, treatments can help manage outbreaks. Similarly, other viral infections can affect the lips, such as hand, foot, and mouth disease, which typically causes sores and blisters on the lips, mouth, and hands, and is most common in young children. Lips can also be affected by fungal infections, such as oral thrush, which is characterized by creamy white patches on the lips and inside the mouth, and angular cheilitis, causing redness, swelling, and cracks in the corners of the mouth.
Bacterial infections can also take hold in the lip area. Impetigo, for example, is a highly contagious bacterial skin infection that often affects the lips and surrounding skin, resulting in blisters and sores. If left untreated, it can lead to more serious complications. Additionally, the lips can be affected by more general skin conditions, such as eczema, psoriasis, and contact dermatitis, all of which can cause dryness, cracking, and inflammation of the lip tissue. In some cases, these conditions may be triggered or exacerbated by specific allergens or irritants, such as certain foods, cosmetics, or environmental factors.
Finally, the lips are also susceptible to various types of cancer, including squamous cell carcinoma and melanoma. These cancers can arise from the lip tissue itself or spread to the lips from other parts of the body. Early warning signs may include persistent sores or discolored patches on the lips that do not heal, and, as with any cancer, early detection and treatment are crucial for the best outcomes. Overall, while the lips are a small part of the body, they can be affected by a wide range of diseases and conditions, and it is important to be vigilant and seek medical advice if any unusual symptoms or changes occur.
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Frequently asked questions
Yes, the lips are composed of multiple layers, one of which is muscle. The muscle layer is called the orbicularis oris muscle, which is a complex of muscles in the lips that encircles the mouth.
The orbicularis oris muscle is the principal muscle of the lips and functions primarily as a sphincter for the oral aperture. It is responsible for lip movement and enables functions such as speech, mastication, and facial expressions. When the orbicularis oris is tonically contracted, the mouth is closed, and when it actively contracts, the mouth orifice becomes narrower, as when kissing or whistling.
The orbicularis oris muscle is the main muscle of the lips, but other muscles that affect the lips include the levator labii superioris, depressor labii inferioris, and platysma.
Diseases that particularly affect the lips include herpes simplex (fever blisters or cold sores), leukoplakia (white patches which may be precancerous), and cancerous ulcers on the vermilion border of the lower lip.
