Blood supply
The lips are very well supplied with blood. The arterial blood flow comes from the facial artery, an outlet from the external carotid artery. The carotid artery branches out again into an upper superior labial artery and a lower inferior labial artery to supply the lips. The venous outflow into the jugular vein takes place via several small veins, which run along the right and left side of the neck and finally flow into the right heart via the superior vena cava.
Innervation
On the lips, the supply by nerves is very pronounced. Since the lips also receive muscle tissue, a motor innervation is required, which is carried out by the facial nerve. It also innervates all other muscles in the face. The lips are also innervated sensitively, which is important for example when touching hot or cold food. The corresponding nerve is the trigeminal nerve (Nervus trigeminus), which is divided into two branches (N. maxillaris and N. mandibularis) in the area of the mouth to supply the upper and lower lip.
Function of the lip
Already in infancy the lips are of great importance. They help to create a tight seal around the female nipple when sucking. The lip muscles make them very flexible and, together with the cheek muscles, form the entrance and exit of the oral cavity.
Due to the very well sensitive innervation of the lips by means of free nerve endings, they are very sensitive to touch. They support the exploration of new and unknown objects already in infancy by often being put into the mouth by the children. The sensitivity to cold and heat is particularly important when eating and thus offers protection against eating too hot food, for example.
The face conveys many different emotions through the different tensing of the muscles. The movement of the lip muscles supports the numerous facial expressions such as smiling when happy, the corners of the mouth drooping when sad or pouting when angry. They are therefore also an important component of non-verbal communication and body language.In addition to the vocal folds in the area of the larynx, the lips are important for the formation of various sounds and the volume.
Their integrated musculature allows some wind instruments to whistle and play. Full round lips are often regarded as a symbol of sensuality and in many cultures they are part of a woman’s ideal of beauty. 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.
