are a visible organ at the mouth of humans and many animals. Both lips are soft, protruding, movable, and serve primarily for food intake, as a tactile sensory organ, and in articulation of speech.
One differentiates between the (''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, having 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 Vessel 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 lip skin is not hairy and does not have
Sweat Gland s or
Sebaceous Gland s. 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.
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.
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.
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
Paniculus 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:
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 .
The lip has many
Nerve Ending s 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.
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 like the trumpet, clarinet, and flute.
''See Full Article:
Facial Expression .''
The lips visibly express emotions.
Because of its high amounts of nerve endings, the lips make an
Erogenous Zone . Lips play a crucial role in
Kissing and other acts of intimacy.
Lips are a visible expression of fertility. It has been shown that the more estrogen a women has the fuller her lips and that full lips are considered attractive.(
lipstick "tricks" men into thinking that a women has more estrogen than she actually has and thus finding her more attractive.[http://www.timesonline.co.uk/article/0,,1072-1894256,00.html
Lips are often viewed as a symbol for sensuality. This has many origins; above all that they are very sensitive as a tactile organ and feel pleasantly soft. It has been suggested that female lips are seen as sexually attractive because they mimic the appearance and sexual swelling of the labia of the vulva, and that the lips are therefore a secondary sex characteristic.
{Link without Title} Additionally, they are a part of the mouth and so are associated with its symbolic connections (see for example
Oral Stage of the psychology according to
Sigmund Freud ).
- 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 misallignment of teeth.
- Cracks or splits in the angles of the lips could be the result of an Inflammation of the lips, Angular Cheilitis .
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.
- 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 of tobacco use.
- Infections from Lip Rings .
Scientific Sources:
# Nozomi Tomiyama, DDS; Toshimichi Ichida, DDS, PhD; Kazunori Yamaguchi, DDS, PhD: Electromyographic Activity of Lower Lip Muscles When Chewing with the Lips in Contact and Apart. ''The Angle Orthodontist'', Vol. 74, No. 1, pp. 31–36. February 2003
# Marcus Bisson, BMed Sci, BM, BS, MRCS; Adriaan Grobbelaar, MBChB, MMed(Plast), FCS(SA), FRCS(Plast): The Aesthetic Properties of Lips: A Comparison of Models and Nonmodels. ''The Angle Orthodontist'', Vol. 74, No. 2, pp. 162–166. June 2003
# McMinn, RMH (Ed) (1994) Last's Anatomy: Regional and applied (9th Ed). London: Churchill Livingstone. ISBN 0-443-04662-X
