One differentiates between the Upper (Labium superioris) and lower lip (Labium inferioris). The lower lip is usually somewhat larger. The border between the lips and the surrounding skin is referred to as the vermilion border, or simply the vermilion. The vertical groove on the upper lip, is known as the philtrum. The entire skin between the upper lip and the nose is referred to as the "ergotrid".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. With light skin color, the lip skin contains no melanocyte (pigment cells, which give skin its color). Because of this, the blood vessels appear through the skin of the lips, which leads to their notable red coloring. With darker skin color this effect is less prominent, as in this case the skin of the lips contains more melanin and thus is visually thicker.The lip skin is not hairy, and does not have sweat glands or sebaceous glands. Therefore, it does not have, the usual protection layer of sweat and body oils which keep the skin smooth, kill pathogens, and regulate warmth. For these reasons, the lips dry out faster and become chapped more easily.
Anatomy in detail The skin of the lips is stratified squamous epithelium. The mucous membrane is represented by a large area in the sensory cortex, and is therefore highly sensitive. The Frenulum Labii Inferioris is the frenulum of the lower lip. The Frenulum Labii Superioris is the frenulum of the upper lip.
Sensory nerve supply Trigeminal nerveThe infraorbital nerve is a branch of the maxillary branch. It supplies not only the upper lip, but much of the skin of the face between the upper lip and the lower eyelid, except for the bridge of the nose. The mental nerve is a branch of the mandibular branch ( via the inferior alveolar nerve). It supplies the skin and mucous membrane of the lower lip and labial gingiva (gum) anteriorly.
Blood supply The facial artery is one of the six non-terminal branches of the external carotid artery. It supplies the lips by its superior and inferior labial branches, each of which bifurcate and anastomose with their companion artery from the other side.
Muscles acting on the lips The muscles acting on the lips are considered part of the muscles of facial expression. All muscles of facial expression are derived from the mesoderm of the second pharyngeal arch, and are therefore supplied (motor supply) by the nerve of the second pharyngeal arch, the facial nerve (7th cranial nerve). The muscles of facial expression are all specialised 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:
Food intake Because they have their own muscles and bordering muscles, the lips are very movable. Lips are used for eating functions, like holding food or to get it in the mouth. In addition, lips serve to close the mouth airtight shut, and to, hold food and drink inside, and to keep out unwanted objects. Through making a narrow funnel with the lips, the suction of the mouth is increased. This suction is essential for babies to breast feed. Lips can also be used to suck in other contexts, such as tactile stimulation of other people.
Erogenous zone Because of their high amounts of nerve endings, the lips are an erogenous zone. The lips therefore play a crucial role in kissing and other acts of intimacy. As the mouth, lips, and tongue are among a woman's most erogenous zones, stimulating a woman's mouth and lips during acts of intimacy has been shown to elicit pleasure and to have a direct stimulatory effect on arousing her genital organs.A woman's lips are also a visible expression of her fertility. In studies performed on the science of human attraction, psychologists have concluded that a woman's facial and sexual attractiveness is closely linked to the makeup of her hormones during puberty and development. Contrary to the effects of testosterone on a man's facial structure, the effects of a woman's estrogen levels serve to maintain a relatively "childlike" and youthful facial structure during puberty and during final maturation. It has been shown that the more estrogen a woman has, the larger her eyes and the fuller her lips. Surveys performed by sexual psychologists have also found that universally, men find a woman's full lips to be more sexually attractive than lips that are less so.A woman's lips are therefore sexually attractive to males because they serve as a biological indicator of a woman's health and fertility. As such, a woman's lipstick (or collagen lip enhancement) takes advantage by "tricking" men into thinking that a women has more estrogen than she actually has, and thus that she is more fertile and attractive.
Tactile organ The lip has many nerve endings and reacts as part of the tactile (touch) senses. Lips are very sensitive to touch, warmth, and, cold. It is therefore an important aide for exploring unknown objects for babies and toddlers.
Articulation The lips serve for creating different sounds - mainly the labial, bilabial, and labiodental consonant sounds - and thus create an important part of the speech apparatus. The lips enable whistling and the performing of wind instruments such as the trumpet, clarinet, and flute.
Facial expressions See Full Article
Symbolic meaningLips are often viewed as a symbol for sensuality and sexuality. This has many origins; above all, the lips are a very sensitive erogenous and tactile organ. Reproductive psychologists have suggested that one reason the female lips are seen as sexually attractive might be because they mimic the appearance and sexual swelling of the labia of the vulva, and that a woman's lips are effectively a secondary sexual organ. This is consistent with research showing male sexual attitudes towards a woman's lips and mouth to be very similar to those towards a woman's vulva. Furthermore, in many cultures of the world, a woman's mouth and lips are veiled because of their representative association with the vulva, and because of their role as a woman's secondary sexual organ.As part of the mouth, the lips are also associated with the symbolism associated with the mouth as orifice by which food is taken in. The lips are also linked symbolically to neonatal psychology(see for example oral stage of the psychology according to Sigmund Freud).
Changes to the lip One of the most frequent changes of the lips is a blue coloring due to cyanosis; the blood contains less oxygen, and thus has a dark red to blue color, which shows through the thin skin. Cyanosis is the reason why corpses always have blue lips. In cold weather cyanosis can appear, so especially in the winter, blue lips may not be an uncommon sight. Lips can (temporarily) swell. The reasons for this are varied and can be from sexual stimulation, injuries and side effects of medications, or misalignment of teeth. Cracks or splits in the angles of the lips could be the result of an inflammation of the lips, Angular cheilitis.
Diseases As an organ of the body, the lip can be a focus of disease or show symptoms of a disease:Lip herpes (technically Herpes labialis, a form of herpes simplex) is a viral infection which appears in the formation of painful blisters at the lip. It's also commonly known as a cold sore. Carcinoma at the lips, is caused predominantly by using tobacco and overexposure of sunlight. To a lesser extent, it could also come from lack of oral hygiene or poor fitting dentures. Alcohol appears to increase the carcinoma risk associated with tobacco use.
A facial expression results from one or more motions or positions of the muscles of the face. These movements convey the emotional state of the individual to observers. Facial expressions are a form of nonverbal communication. They are a primary means of conveying social information among humans, but also occur in most other mammals and some other animal species. Humans can adopt a facial expression as a voluntary action. However, because expressions are closely tied to emotion, they are more often involuntary. It can be nearly impossible to avoid expressions for certain emotions, even when it would be strongly desirable to do so; a person who is trying to avoid insult to an individual he or she finds highly unattractive might nevertheless show a brief expression of disgust before being able to reassume a neutral expression. The close link between emotion and expression can also work in the other direction; it has been observed that voluntarily assuming an expression can actually cause the associated emotion. Some expressions can be accurately interpreted even between members of different species- anger and extreme contentment being the primary examples. Others, however, are difficult to interpret even in familiar individuals. For instance, disgust and fear can be tough to tell apart. Because faces have only a limited range of movement, expressions rely upon fairly minuscule differences in the proportion and relative position of facial features, and reading them requires considerable sensitivity to same. Some faces are often falsely read as expressing some emotion, even when they are neutral, because their proportions naturally resemble those another face would temporarily assume when emoting.
Universality Charles Darwin noted in his book The Expression of the Emotions in Man and Animals: ...the young and the old of widely different races, both with man and animals, express the same state of mind by the same movements. Still, up to the mid-20th century most anthropologists believed that facial expressions were entirely learned and could therefore differ among cultures. Studies eventually supported Darwin's belief to a large degree, particularly for expressions of anger, sadness, fear, surprise, disgust, contempt, happiness and caring.(citation needed) The people of New Guinea called South Fore were chosen as subjects for one such survey. The study consisted of 189 adults and 130 children from among a very isolated population, as well as twenty three members of the culture who lived a less isolated lifestyle as a control group. Participants were told a story that described one particular emotion; they were then shown three pictures (two for children) of facial expressions and asked to match the picture which expressed the story's emotion. While the isolated South Fore people could identify emotions with the same accuracy as the non-isolated control group, problems associated with the study include the fact that both fear and surprise were constantly misidentified. The study concluded that certain facial expressions correspond to particular emotions, regardless of cultural background, and regardless of whether or not the culture has been isolated or exposed to the mainstream.
Communication A person's face, especially their eyes, creates the most obvious and immediate cues that lead to the formation of impressions. This article discusses eyes and facial expressions and the effect they have on interpersonal communication. A person's eyes reveal much about how they are feeling, or what they are thinking. Blink rate can reveal how nervous or at ease a person may be. Research by Boston College professor Joe Tecce suggests that stress levels are revealed by blink rates. He supports his data with statistics on the relation between the blink rates of presidential candidates and their success in their races. Tecce claims that the faster blinker in the presidential debates has lost every election since 1980. Though Tecce's data is interesting, it is important to recognize that non-verbal communication is multi-channeled, and focusing on only one aspect is reckless. Nervousness can also be measured by examining each candidates' perspiration, eye contact and stiffness. Eye contact is another major aspect of facial communication. Some have hypothesized that this is due to infancy, as humans are one of the few mammals who maintain regular eye contact with their mother while nursing. Eye contact serves a variety of purposes. It regulates conversations, shows interest or involvement, and establishes a connection with others. Eye contact regulates conversational turn taking, communicates involvement and interest, manifests warmth, and establishes connections with others and it can command attention, be flirtatious, or seem cold and intimidating it invites conversation. Lack of eye contact is usually perceived to be rude or inattentive. But different cultures have different rules for eye contact. Certain Asian cultures can perceive direct eye contact as a way to signal competitiveness, which in many situations may prove to be inappropriate. Others lower their eyes to signal respect, but in western cultures this could be misinterpretted as lacking self-confidence. Even beyond the idea of eye contact, our eyes communicate more data than we even consciously express. Pupil dilation is a significant cue to a level of excitment, pleasure, or attraction. Dilated pupils indicate greater affection or attraction, while constricted pupils send a colder signal. The face as a whole indicates much about our moods as well. Specific emotional states, such as happiness or sadness, are expressed through a smile or a frown, respectively. There are seven universally recognized emotions shown through facial expressions: fear, anger, surprise, contempt, disgust, happiness, and sadness. Regardless of culture, these expressions are the same. However, the same emotion from a specific facial expression may be recognized by a culture, but the same intensity of emotion may not be perceived. For example, studies have shown that Asian cultures tend to rate images of facial emotions as less intense than non-Asian cultures surveyed. This difference can be explained by display rules, which are culture-specific guidelines for behavior appropriateness. In some countries, it may be more rude to display an emotion than in another. Showing anger toward another member in a group may create problems and disharmony, but if displayed towards a competitive rival, it could create in-group cohesion.
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