What is lips

B1 [ C ] one of the two soft parts that form the upper and lower edges of the mouth :. She kissed me on the lips. He licked his lips. Her lower lip trembled as if she was about to cry. She took a bite of doughnut and licked her lips. She put on her lipstick and then carefully blotted her lips with a tissue. There was the faintest trace of a smile on his lips. Her hair was jet-black , her lips ruby-red, and her skin as white as snow.

That's enough of your lip! Rude and cheeky. Idioms my lips are sealed. Lip gloss. Time Traveler for lip The first known use of lip was before the 12th century See more words from the same century. Style: MLA. More Definitions for lip. English Language Learners Definition of lip. Kids Definition of lip. Medical Definition of lip. Get Word of the Day daily email!

Test Your Vocabulary. Can you spell these 10 commonly misspelled words? Love words? Darwin himself noted that there are cultures in which kissing is conspicuously absent. If kissing isn't universal, it could still have its roots in biology, perhaps as a combination of inherited impulses and learned behaviour. For one thing, other species kiss as well. Chimpanzees do it in order to reconcile following a fight, and bonobos do it with some tongue as well.

In a issue of Scientific American Mind the writer Chip Walter argued, citing British zoologist Desmond Morris, that kissing may have originated from the primate behavior of pre-chewing food and passing it to the kids.

Chimpanzee mothers, for example, are known to chew food and before swallowing they press their lips to the lips of their youngsters to allow the food to pass into their mouths.

The pressing of lips may have then become a general means for relieving anxiety. Basic classical conditioning would suggest that by pairing lip stimulation with food, simply touching the lips would eventually trigger feelings of pleasure. Add to that the overabundance of nerve endings in the lips, and you have the recipe for ecstasy. Lips are exquisitely sensitive if sometimes slimy bits of tissue.

The part of the brain responsible for detecting touch is called the somatosensory cortex, and is found on the top of the brain in an area called the postcentral gyrus. Touch sensations from all over the body get sent there to be processed, with each part of the body getting its own little sub-division along the postcentral gyrus, and the size reflects the density of receptors rather than the amount of skin available to touch.

For example, the part devoted to sensations from the chest and stomach is fairly small. The lip has many nerve endings and reacts as part of the tactile senses. Lips are very sensitive to touch, warmth and cold. Because of their high number of nerve endings, the lips are an erogenous zone. The lips therefore play a crucial role in osculation and other acts of intimacy. The upper lip lies between the nose and the orifice of the oral cavity.

Laterally the lips are separated from the cheeks by the nasolabial grooves that extend from the nose and pass approximately 1 cm lateral to the angles of the mouth. These grooves or folds are easier to observe when smiling. The upper lip has an infranasal depression, the philtrum Greek for love-charm , that extends from the external nasal septum, separating the nostrils, to the vermillion border — the sharp demarcation between the coloured edge of the lip and surrounding skin.

The lower lip lies between the mouth and the labiomental groove , which separates the lower lip form the chin [1]. The upper and lower lips are continuous at the angles of the mouth or oral commissures Table 1.

In adults the outer lip skin is thicker and contains hair, sweat glands, and sebaceous glands. The edges of the lips are covered with reddish skin, called the vermillion, and are abundantly provided with sensitive nerve endings. The vermillion is a transition layer between the outer, hair-bearing tissue and the inner mucous membrane. The skin of the vermillion is made up of three to five cellular layers and is very thin compared to the skin on the rest of the face, which is typically arranged in 16 cellular layers.

The mucous membrane of the lip is full of capillaries that are close to the translucent surface of the vermillion, giving it its characteristic reddish colour. In newborn infants the inner surface is much thicker, with sebaceous glands and minute projections called papillae. These structural adaptations seem to aid the process of sucking [4]. The upper lip labium superioris is superior in name only since it is actually somewhat smaller than its partner, the lower lip labium inferioris.

In an ideal world, the lower lip vermillion show should be Phi times greater than the upper vermillion. However, that ratio can vary dramatically with ethnic background, and even from individual to individual within the same ethnic group. Therefore, it does not have the usual protective layer of sweat and body oils which keep the skin smooth, inhibit pathogens, and regulate warmth.

For these reasons, the lips dry out faster and become chapped more easily. The skin of the lips is categorised as stratified squamous epithelium, or flattened tissue cells. The outer lip skin is keratinised stratified squamous epithelium with numerous hair follicles. As the epithelium approaches the so-called red area of the lip, the epithelium becomes non-keratinised stratified squamous epithelium.

This type of epithelium is designed for protection and lubrication during chewing and swallowing. Figure 2: Anatomy of normal orbicularis oris muscle: pars marginalis blue and pars peripheralis red. The orbicularis oris muscle, the lip muscle, is a broad elliptical muscle around the mouth Figure 2. When the orbicularis oris is tonically contracted, the mouth is closed, whereas active phasic contraction causes the mouth orifice to become narrower as when kissing or whistling.

Its lateral fibres join the modiolus, a chiasma of facial muscles held together by fibrous tissue, located lateral and slightly superior to each angle of the mouth.

Orbicularis oris consists of two distinct parts, the pars marginalis and pars peripheralis , which differ in location and function [5]. Anatomical studies have shown that pars peripheralis fibres decussate at midline and insert into the contralateral philtral ridge, whereas pars marginalis fibres form a continuous band from modiolus to modiolus.