Lip

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Lip
Human lips
Details
Artery	inferior labial, superior labial
Vein	inferior labial, superior labial
Nerve	frontal, infraorbital
Identifiers
Latin	labia oris
MeSH	D008046
TA98	A05.1.01.005
TA2	2775
FMA	59816
Anatomical terminology [edit on Wikidata]

The lips are a horizontal pair of

Structure

The upper and lower lips are referred to as the labium superius oris and labium inferius oris, respectively.

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 fewer

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.

Nerve supply

• Trigeminal nerve
  • The infraorbital nerve is a branch of the maxillary branch. It supplies not only the upper lip but also much of the skin of the face between the upper lip and the lower eyelid, except for the bridge of the nose.
  • The
    gingiva
    (gum) anteriorly.

Blood supply

The facial artery is one of the six non-terminal branches of the external carotid artery.

This artery supplies both lips by its superior and inferior labial branches. Each of the two branches bifurcate and anastomose with their companion branch from the other terminal.

Muscles

The muscles acting on the lips are considered part of the muscles of

• Buccinator
• Orbicularis oris (a complex of muscles, formerly thought to be a single sphincter or ring of muscle)
• Anchor point for several muscles
  • Modiolus
• Lip elevation
  • Levator labii superioris
  • levator labii superioris alaeque nasi
  • Levator anguli oris
  • Zygomaticus minor
  • Zygomaticus major
• Lip depression
  • Risorius
  • Depressor anguli oris
  • Depressor labii inferioris
  • Mentalis

Functions

Food intake

Because they have their own muscles and bordering muscles, the lips are easily 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, to hold food and drink inside, and to keep out unwanted objects. Through making a narrow

Articulation

The lips serve for creating different sounds—mainly labial, bilabial, and labiodental consonant sounds as well as vowel rounding—and thus are an important part of the speech apparatus. The lips enable whistling and the performing of wind instruments such as the trumpet, clarinet, flute, and saxophone. People who have hearing loss may unconsciously or consciously lip read to understand speech without needing to perceive the actual sounds, and visual cues from the lips affect the perception of what sounds have been heard, for example the McGurk effect.

Tactile organ

The lip has many

Because of their high number of nerve endings, the lips are an

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

Lip size is linked to sexual attraction in both men and women. Women are attracted to men with masculine lips that are more middle size and not too big or too small; they are to be rugged and sensual. In general, the researchers found that a small nose, big eyes and voluptuous lips are sexually attractive both in men and women.[11] The lips may temporarily swell during sexual arousal due to engorgement with blood.^{[medical citation needed]}

Facial expression

The lips contribute substantially to facial expressions. The lips visibly express emotions such as a smile or frown, iconically by the curve of the lips forming an up-open or down-open parabola, respectively. Lips can also be made pouty when whining or perky to be provocative.

Clinical significance

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As an organ of the body, the lip can be a focus of disease or show symptoms of a disease:

• 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 sometimes have blue lips. In cold weather cyanosis can appear, so especially in the winter, blue lips may not be an uncommon sight.^[12]
• Inflammation of the lips is termed
  herpes simplex) and actinic cheilitis (chronically sun damaged lips).^[13]

• Cleft lip is a type of birth defect that can be successfully treated with surgery.^[14]
• basocellular carcinoma.^[17]

Lips are often viewed as a symbol of sensuality and sexuality. This has many origins; above all, the lips are a very sensitive erogenous and tactile organ. 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.^[18]

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).

Lip piercing or lip augmentation is sometimes carried out for cosmetic reasons. Products designed for use on the lips include lipstick, lip gloss and lip balm.

Other animals

In most vertebrates, the lips are relatively unimportant folds of tissue lying just outside the jaws. However, in

• Stiff upper lip

References