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Lips are a visible body part at the mouth of humans and many animals. Lips are soft, movable, and serve as the opening for food intake, as an erogenous organ used in kissing and other acts of intimacy, as a tactile sensory organ, and in the articulation of speech.

differentiates between the Upper (Labia superfluos entafada) and lower lip (Labium inferius).






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Lips are a visible body part at the mouth of humans and many animals. Lips are soft, movable, and serve as the opening for food intake, as an erogenous organ used in kissing and other acts of intimacy, as a tactile sensory organ, and in the articulation of speech.

Anatomical basics of the human lip

One differentiates between the Upper (Labia superfluos entafada) and lower lip (Labium inferius). 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
Philtrum

The philtrum , also known as the infranasal depression is the vertical groove in the upper lip, formed where the nasomedial and Maxillary_prominence processes meet during embryonic development....
.

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 melanocytes (cells which produce melanin pigment
Pigment

A pigment is a material that changes the color of light it Reflection as the result of selective color absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which the material itself emits light....
 , which give skin its color). Because of this, the blood vessel
Blood vessel

The blood vessels are the part of the circulatory system that transport blood throughout the body. There are three major types of blood vessels: the artery, which carry the blood away from the heart, the capillary, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from...
s 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 skin of the lip forms the border between the exterior skin of the face, and the interior mucous membrane
Mucous membrane

The mucous membranes are linings of mostly germ layer origin, covered in epithelium, which are involved in absorption and secretion. They line various body cavities that are exposed to the external environment and internal organ ....
 of the inside of the mouth.

The lip skin is not hairy, and does not have sweat gland
Sweat gland

The skin contains two different groups of sweat glands: apocrine sweat glands and merocrine sweat glands. Both gland types contain myoepithelial cells , specialized epithelial cells located between the gland cells and the underlying basal lamina....
s or sebaceous gland
Sebaceous gland

Sebaceous glands are small glands in the skin which secrete an oily matter in the hair follicles to lubricate the skin and hair of animals. In humans, they are found in greatest abundance on the face and scalp, though they are distributed throughout all skin sites except the palms and soles....
s. Therefore it does not have the usual protection 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.

Anatomy in detail

The skin
Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
 of the lips is stratified squamous epithelium. The mucous membrane is represented by a large area in the sensory cortex
Somatosensory system

The somatosensory system is a diverse sensory system comprising the receptors and processing centres to produce the sensory modality such as touch, temperature perception, proprioception , and nociception ....
, and is therefore highly sensitive. The Frenulum Labii Inferioris is the frenulum
Frenulum

A frenulum is a small fold of tissue that secures or restricts the motion of a mobile organ in the body....
 of the lower lip. The Frenulum Labii Superioris is the frenulum of the upper lip.

Sensory nerve supply

  • Trigeminal nerve
    Trigeminal nerve

    The trigeminal nerve is responsible for sensation in the face. Sensory information from the face and body is processed by parallel pathways in the central nervous system....
    • The infraorbital nerve
      Infraorbital nerve

      After the maxillary nerve enters the infraorbital canal, the nerve is frequently called the infraorbital nerve. This nerve innervates the lower eyelid, upper lip, and part of the vestibule and exits the infraorbital foramen of the maxilla....
       is a branch of the maxillary
      Maxillary

      Maxillary is something related to the maxilla bone. It may be:*Maxillary artery*Maxillary nerve*Maxillary prominence*Maxillary sinus...
       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
      Nose

      Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for Respiration in conjunction with the mouth....
      .
    • The mental nerve
      Mental nerve

      The mental nerve is a general somatic afferent nerve which provides sensation to the anterior aspects of the chin and lower lip as well as the buccal gingivae of the mandibular anterior teeth and the premolars....
       is a branch of the mandibular
      Mandible

      The mandible or inferior maxillary bone forms the lower jaw and holds the lower tooth in place. It also refers to both the upper and lower sections of the beaks of birds....
       branch ( via the inferior alveolar nerve
      Inferior alveolar nerve

      The inferior alveolar nerve is a branch of the mandibular nerve, which is itself the third branch of the trigeminal nerve ....
      ). It supplies the skin and mucous membrane of the lower lip and labial gingiva
      Gingiva

      The gingiva , or gums, consists of the mucosal tissue that lies over the alveolar bone....
       (gum) anteriorly.


Blood supply

The facial artery
Facial artery

The facial artery is a branch of the external carotid artery that supplies structures of the face....
 is one of the six non-terminal branches of the external carotid artery
External carotid artery

In human anatomy, the external carotid artery is a major artery of the head and neck. It arises from the common carotid artery when it bifurcates into an internal and external branch....
. 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
Facial expression

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....
. All muscles of facial expression are derived from the mesoderm
Germ layer

A germ layer is a group of cell s, formed during animal embryogenesis. Germ layers are particularly pronounced in the vertebrates; however, all animals more complex than sea sponge produce two or three primary tissue layers ....
 of the second pharyngeal arch, and are therefore supplied (motor supply) by the nerve of the second pharyngeal arch, the facial nerve
Facial nerve

The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla oblongata, and controls the muscles of facial expression, and taste to the anterior two-thirds of the tongue....
 (7th cranial nerve). The muscles of facial expression are all specialized members, of the panniculus carnosus
Panniculus carnosus

The panniculus carnosus is a part of the subcutaneous tissue, a vestigial layer of striated muscle deep to the panniculus adiposus....
, which attach to the dermis
Dermis

File:EpidermisPainted.svgThe dermis is a layer of skin between the epidermis_ and subcutaneous tissues, and is composed of two layers, the papillary_dermis and reticular dermis....
 and so wrinkle, or dimple the overlying skin. Functionally, the muscles of facial expression are arranged in groups around the orbits
Orbit (anatomy)

In anatomy, the orbital bone is the cavity or socket of the skull in which the eye and its adnexa are situated.It can also mean the skin which surrounds the eye of a bird....
, nose
Nose

Anatomically, a nose is a protuberance in vertebrates that houses the nostrils, or nares, which admit and expel air for Respiration in conjunction with the mouth....
 and mouth
Mouth

The mouth, buccal cavity, or oral cavity is the first portion of the alimentary canal that receives food and begins digestion by mechanically breaking up the solid food particles into smaller pieces and mixing them with saliva....
.

The muscles acting on the lips:
  • sphincter
    Sphincter

    A sphincter is a structure, usually a circular muscle, that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning....
    s of the oral orifice
    • buccinator
      Buccinator muscle

      The buccinator is a thin quadrilateral muscle, occupying the interval between the maxilla and the mandible at the side of the face.Action...
    • orbicularis oris
      Orbicularis oris muscle

      In human anatomy, the orbicularis oris muscle is the sphincter muscle around the mouth.It is also one of the muscles used in the playing of all brass instruments and some woodwind instruments....
  • anchor point for several muscles
    • modiolus
      Modiolus (anatomy)

      In facial anatomy, the modiolus is a chiasma of facial muscles held together by fibrous tissue, located lateral and slightly superior to each angle of the mouth....
  • lip elevation
    • levator labii superioris
      Levator labii superioris

      The levator labii superioris is a broad sheet, the origin of which extends from the side of the nose to the zygomatic bone.Its medial fibers form the angular head, which arises by a pointed extremity from the upper part of the frontal process of the maxilla and passing obliquely downward and lateralward divides into two slips....
    • levator labii superioris alaeque nasi
      Levator labii superioris alaeque nasi muscle

      The levator labii superioris alaeque nasi muscle is, translated from Latin, the "lifter of the upper lip and of the wing of the nose". It has the longest name of any muscle in an animal....
    • levator anguli oris
      Levator anguli oris

      The levator anguli oris is a Facial muscles muscle of the mouth arising from the canine fossa, immediately below the infraorbital foramen.Its fibers are inserted into the angle of the mouth, intermingling with those of the Zygomaticus, Triangularis, and Orbicularis oris....
    • zygomaticus minor
      Zygomaticus minor muscle

      The zygomaticus minor is a muscle of facial expression. It originates from M. orbicularis oculi on the lateral face of the zygomatic bone and then inserts on the upper lip....
    • zygomaticus major
      Zygomaticus major muscle

      The Zygomatic major is a muscle of the human body. It is a muscle of facial expression which draws the angle of the mouth superiorly and posteriorly....
  • lip depression
    • risorius
      Risorius

      The risorius arises in the fascia over the parotid gland and, passing horizontally forward, superficial to the platysma, inserts onto the skin at the angle of the mouth....
    • depressor anguli oris
      Depressor anguli oris muscle

      The Depressor anguli oris arises from the oblique line of the mandible, whence its fibers converge, to be inserted, by a narrow fasciculus, into the angle of the mouth....
    • depressor labii inferioris
      Depressor labii inferioris muscle

      The depressor labii inferioris is a facial muscle that helps lower the bottom lip....
    • mentalis
      Mentalis

      The Mentalis is situated at the tip of the chin. It raises and pushes up the lower lip, causing wrinkling of the chin, as in doubt or displeasure....


Functions of 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 sucking on a straw to drink liquids.

Erogenous zone

Because of their high amounts of nerve endings, the lips are an erogenous zone
Erogenous zone

An Erogenous zone is an area of the human body that has heightened sensitivity and stimulation of which normally results in human sexual response....
. The lips therefore play a crucial role in kissing and other acts of intimacy.

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
Testosterone

Testosterone is a steroid hormone from the androgen group. In mammals, testosterone is primarily secreted in the testis of males and the ovaries of females, although small amounts are also secreted by the adrenal glands....
 on a man's facial structure, the effects of a woman's oestrogen levels serve to maintain a relatively "childlike" and youthful facial structure during puberty and during final maturation. It has been shown that the more oestrogen 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
Collagen

Collagen is the main protein of connective tissue in animals and the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content....
 lip enhancement) takes advantage by "tricking" men into thinking that a woman has more oestrogen 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 aid for exploring unknown objects for babies and toddlers.

Articulation

The lips serve for creating different sounds - mainly the labial
Labial consonant

Labials are consonants articulated either with both lips or with the lower lip and the upper teeth . English is a bilabial nasal consonant sonorant, and are bilabial stop consonant , and are labiodental fricative consonant....
, bilabial
Bilabial consonant

In phonetics, a bilabial consonant is a consonant articulated with both lips. The bilabial consonants identified by the International Phonetic Alphabet are:...
, and labiodental consonant
Labiodental consonant

In phonetics, labiodentals are consonants Place of articulation with the lower lip and the upper teeth. The labiodental consonants identified by the International Phonetic Alphabet are:...
 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

The lips visibly express emotions such as a smile or frown. Lips can also be made pouty when whining, or perky to be provocative.

Symbolic meaning

Lips 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. 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
Oral stage

The oral stage in psychoanalysis is the term used by Sigmund Freud to describe his theory of child development during the first 18 months of life, in which an infant's pleasure centers are in the mouth....
 of the psychology according to Sigmund Freud
Sigmund Freud

Sigmund Freud , born Sigismund Schlomo Freud , was an Austrian psychiatrist who founded the psychoanalysis of psychology. Freud is best known for his theories of the unconscious mind and the defense mechanism of Psychological repression and for creating the clinical practice of psychoanalysis for curing psychopathology through dialogue...
).

Changes to the lip

  • One of the most frequent changes of the lips is a blue coloring due to cyanosis
    Cyanosis

    Cyanosis is a blue coloration of the skin and mucous membranes due to the presence of > 5g/dl deoxygenated hemoglobin in blood vessels near the skin surface....
    ; 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
    Inflammation

    Inflammation is the complex biological response of Blood vessel tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. It is a protective attempt by the organism to remove the injurious stimuli as well as initiate the healing process for the tissue....
     of the lips, Angular cheilitis
    Angular cheilitis

    Angular cheilitis is an inflammatory lesion at the labial commissure, or corner of the mouth, and often occurs bilaterally. The condition manifests as deep cracks or splits....
    .


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
    Herpes simplex

    Herpes simplex is a viral disease caused by Herpes simplex viruses; both herpes simplex virus 1 and herpes simplex virus 2 cause 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
    Carcinoma

    A carcinoma is any malignant cancer that arises from Epithelium. Carcinomas invade surrounding tissues and organs and may Metastasis, or spread, to lymph nodes and other sites....
     (a malignant cancer that arises from epithelial cells) 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
    Oral hygiene

    Teeth cleaning is the removal of dental plaque from teeth, in order to prevent Dental caries , gingivitis, and Periodontal disease. It is part of a complete program of oral hygiene....
     or poor fitting dentures. Alcohol appears to increase the carcinoma risk associated with tobacco use.


Literature

Scientific Sources:

See also

  • Kiss
    Kiss

    A kiss is the touching of one person's lip s to another place, which is used as an expression of affection, respect, greeting, wiktionary:farewell, good luck, romantic affection or sexual desire....
  • Lipstick
    Lipstick

    Lipstick is a cosmetics containing pigments, oils, waxes, and emollients that applies color and texture to the lip . There are many varieties of lipstick....
  • Lip gloss
    Lip gloss

    Lip gloss is a Cosmetics product used primarily to give lips a mildly glossy lustre and sometimes subtle color. It is distributed as a liquid or a soft solid ....
  • Lip balm
    Lip balm

    Lip balm or lip salve is a substance topically applied to the lips of the mouth to relieve chapped or dry lips, angular cheilitis or stomatitis, and Herpes simplex virus....
  • Lip piercing
    Lip piercing

    A lip piercing is a type of body piercing that penetrates the lips or the area surrounding the lips, which can be pierced in a variety of ways....
  • Facial expression
    Facial expression

    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....
  • Herpes
  • Chapped lips
    Chapped lips

    Chapped lips is a condition whereby the lips become dry and possibly cracked. It may be caused by the evaporation of moisture....
  • Cupid's bow
    Cupid's bow

    Cupid's bow is a facial feature where the double curve of a human upper lip is said to resemble the bow of the Cupid, the Roman god of erotic love....
  • Cleft lip


Additional images


External links