The lips consist of an upper lip (Labium superius) and a lower lip (Labium inferius). At the right and left corner of the mouth (Angulus oris) the lips merge. They contain muscle tissue and the crack in the mouth (Rima oris) forms the entrance to the oral cavity. On the inside they have an upper and lower lip frenulum (Frenulum labii superioris et inferioris), a connection to the jaw.


The lips can be divided macroscopically into two different types of tissue.

On the outside there is skin that merges into the mucous membrane on the inside. It can be divided into 3 sections, which flow smoothly into one another, so that a clear border is not recognizable.
The outer skin (Pars cutanea) consists of a multilayered keratinized squamous epithelium and forms a protective barrier to the outside world. It is characteristically made up of several layers of cells lying on top of one another. Hair follicles, sebum glands (to keep the lips supple) and sweat glands are located in these cell layers and the underlying tissue. The cornification is caused by dying special cells that Keratinocytes to be named.
The transition zone in which the actual lip red is located lies between the inside and outside. This area will too Pars intermedia called. This area also contains keratinized squamous epithelium, which is significantly thinner compared to the anterior zone. The connective tissue protrudes into the squamous epithelium; this is called the lamina propria directly below the cell layers. Many arterial capillaries run here that shine through the thin upper layer. This creates the strong red color of the lips. When the oxygen content in these capillary loops drops, the typical phenomenon of blue lips (cyanosis) occurs.

The inner layer is lined with mucosal epithelium, an uncornified squamous epithelium. In addition to numerous vessels and nerve fibers, there are particularly many small salivary glands that form a viscous (mucous) Produce saliva. This keeps the lips moist and, like the larger salivary glands, is responsible for breaking down the food ingested.
Under this layer lies the muscle of the lips (Orbicularis oris muscle) embedded in the connective tissue. This is responsible for the movement of the lips.

Blood supply

The lips are very well supplied with blood. They receive the arterial blood flow from the Facial artery, an exit from the carotid artery (External carotid artery). This branches off again into an upper one Superior labial artery and a lower one Inferior labial artery to Care of the lips on.
The venous drainage into the takes place via several small veins Jugular veinthat run right and left in the neck and finally over the superior vena cava (Superior vena cava) flow into the right heart.


The supply is through on the lips annoy very pronounced. Since the lips also contain muscle tissue, you need one motor innervationpassing through the facial nerve (Facial nerve) he follows. He also innervates everyone other muscles in the face.
The lips will also sensitively innervatedwhich is important for, for example, touching hot or cold food. The associated nerve is the Trigeminal nerve (Trigeminal nerve), which is divided into two branches in the area of ​​the mouth (Maxillary and mandibular nerves) divided to supply the upper and lower lip.

Function of the lip


Even in infancy, the lips are of great importance. When sucking, they help to seal the female nipple tightly all around. The muscles of the lips make them very flexible and, together with the muscles of the cheek, form the entrance and exit of the oral cavity.

Organ of touch

The very sensitive innervation of the lips by means of free nerve endings makes them very sensitive to touch. They support the exploration of new, unknown objects even in toddler age, as they are often put in the mouth by the children. The sensitivity to cold and heat is particularly important when eating and thus offers protection against eating too hot, for example.

facial expressions

The face conveys many different emotions by tensing the muscles in different ways. The movement of the lip muscles supports the numerous facial expressions such as smiling when happy, drooping the corners of the mouth when sad or pouting when angry. They are therefore also an important part of non-verbal communication and body language.

Language education

In addition to the vocal folds in the area of ​​the larynx, the lips are important for the formation of various sounds and volume. Your integrated musculature allows you to whistle and play some wind instruments.


Full, round lips are often seen as a symbol of sensuality and are part of the woman's ideal of beauty in many cultures. The importance for sexuality becomes particularly clear when kissing. Due to the numerous nerve endings, they form a stimulating zone for many people and convey sexual excitability.

Lip frenulum

The Lip frenulum is in the jargon Frenulum labii called and located on the inside of the Upper lip. There it is in the middle of the upper one Incisors. It is a connective tissue structure, however no important task performed. The lip frenulum is just a leftover.

A too pronounced lip frenulum can cause problems in the mouth. For example, this often results in a Tooth gapthat can be accompanied by speech defects such as lisp. In this case, surgical transection of the lip frenulum is usually carried out in childhood.

If there are no more teeth in the jaw, the lip frenulum can have a negative effect on the fit of the prosthesis.

It should also be removed if it is very high in Gums is anchored and creates an uncomfortable pull in the movement of the lip.

Diseases of the lip

Herpes labialis

One of the most common diseases affecting the lips is infection with the herpes simplex virus. After the initial infection, this migrates along the nerve fibers to form an accumulation of nerve cell bodies, the so-called Gangliathat sit deeper in the head. The virus can be reactivated during menstruation or stress-induced and migrates along the nerve fiber to the lip, where it triggers an inflammatory reaction in the form of burning and itchy blisters.
Anyone who has ever had such an infection can get it more often. In contrast, many people also carry the virus within them without an outbreak of the infection. You can still carry the virus through contact, which can then trigger a reaction in the form of the symptoms described above in the newly infected person.

Cleft lip and palate

The cleft lip and palate is a malformation that has existed since birth in the area of ​​the lip and the philtrum, the region between the upper lip and nose. The cleft palate develops during the development of the embryo between the 5th and 7th week of pregnancy. Right and left nasal bulges emerge from the embryonic appendages, which merge into the upper lip in the course of growth. This can lead to disturbances which can affect the upper lip alone or at the same time as the upper jaw and the palate. Depending on how severe the malformation is, the malformation can be remedied with very good cosmetic success after the birth.


Another possible disease on the lips is that Malignancy, a malignant change mostly on the lower lip. It initially expresses itself as a precancerous stage (Precancerous disease) and is called leukoplakia, a whitish change in the mucous membrane of the lip that cannot be wiped off and that extends over an ulcer to the carcinoma can develop further. Other symptoms include swelling and pain in the lip area.
A comprehensive examination of the surrounding lymph nodes, the tongue and the adjoining throat area and possibly the food duct is recommended. Common causes are excessive consumption of tobacco and alcohol. Poor oral hygiene or exposure to sunlight can also encourage ulcer development. Depending on the severity and stage of the disease, an adapted therapy is selected that includes treatment with cytostatics and / or surgery. In most cases, the change on the lips is noticed very early on by the patient, so that there is a good chance of recovery.

Swollen lip

Lip swelling can be caused by different causes and its treatment can also vary.

Read more about the topic here: Swollen lip

Read more on the topic: Bruise on the lip