The levator labii superioris muscle is a striated muscle of the facial muscles. The main task of the muscle is the upward movement of the upper lip. Lesions of the facial nerve paralyze the levator labii superioris muscle.

What is the levator labii superioris muscle?

The skeletal muscles consist of striated muscles and are largely responsible for the motor function of the human skeleton. Most skeletal muscles have direct contact with the bones. An exception are the so-called skin muscles.

This muscle group is only slightly pronounced in humans. The muscles of the human skin mainly include some muscles of facial expression. One of these muscles is the lavator labii superioris muscle. As the Latin name implies, this mimic muscle is the so-called upper lip lift. Like all skin muscles, the lavator labii superioris muscle does not sit directly on the human skeleton. Skin muscles are much more between the fascia and the skin.

The mimic muscle lies in the front cheek area on the nose slope and consists of a course of different fiber strands: from the Caput angulare, the Caput infraorbitale and the Caput zygomaticum. Different literature refers only to the infraorbital caput as the lavator labii superioris muscle and treats the other fiber strands as distinct muscle fibers.

Anatomy & Construction

Striated muscle like the lavator labii superioris muscle is always composed of filaments of myosin and actin. These contractile filaments overlap at different sites and are also referred to as contractile muscle components.

The levator labii superioris muscle is attached to the nervous system by the Rami buccales and Rami zygomatici of the VII. Cranial nerve (facial nerve). The caput angulare corresponds to the medial fiber strands of the muscle and forms the musculus levator labii superioris alaeque nasi originating at the processus frontalis. The cord runs obliquely downwards and becomes caudal to two parts of the fibers, which attach themselves to alar cartilage (Cartilago alaris major) and nose wing skin.

Another part of the fiber supplies the lateral upper lip and meets the orbicularis oris muscle. The middle parts of the upper lip lift correspond to the infraorbital caput and originate from the lower orbital rim above the infraorbital foramen. The fibers reach the upper lip muscles between canine and caput angulare. The lateral portion of the upper lip lifter is the zygomatic caputum, which corresponds to the zygomaticus minor muscle and originates from the medial upper lip of the osseous surface of the zygomatic bone.

Function & Tasks

Although the lavator labii superioris muscle is a skeletal muscle, unlike other skeletal muscles, its functions are not in the bone movement. Instead of bone motor, the muscle is responsible for the motor movements of the face and is counted for these reasons to mimic muscles. Mimicry plays a key role in human communication. For example, where verbal communication creates misunderstandings, a smile or a nose can create clarity.

Since mimic expression is a natural basic expression of humans, facial expressions are understood as early as infancy. The contraction of the lavator labii superioris muscle raises the upper lip. The upturned upper lip can signal disgust, for example. This is especially true when at the same time pushes the lower lip forward. Visible wrinkles form during the movement between the corners of the mouth and the nasal angles. Often at the same time the nose is rumbled. The contraction of the lavator labii superioris muscle is triggered by the facial nerve, the seventh cranial nerve responsible for the motor attachment of many facial muscles to the central nervous system.

In addition to the motor, the nerve also contains sensitive, parasympathetic and sensory fiber qualities. The mimic function of the upper lip lift muscle is therefore more correctly described as a function of the neuromuscular complex of the facial nerve and the lavator labii superioris muscle. Mimic movements such as an upturned upper lip often reveal conversational attitudes and spontaneous emotions that have never been uttered.

Diseases

Like any other muscle, the lavator labii superioris muscle may be affected by a variety of muscular and neuromuscular disorders. For example, degenerative muscle disease is myopathy, which is associated with muscle weakness and muscle tremors. This phenomenon can be triggered by various influences.

In addition to genetic causes, for example, poisoning can play a role, for example in alcohol myopathy. To be distinguished from muscular weaknesses is the paralysis of the lavator labii superioris muscle. Paralyzes of the structure are caused by lesions of the facial nerve and usually do not appear as isolated signs of paralysis. Most other facial muscles are impaired by the so-called facial paresis in their function. The facial nerve can be damaged by different diseases. The damage can occur both in the peripheral and central area of ​​the cranial nerve.

In addition to infectious diseases such as Lyme disease or Zoster oticus mechanical effects such as the temporal bone fracture and tumors may be responsible for a peripheral damage to the nerve. On the other hand, central damage is caused by cerebral hemorrhages, autoimmune and bacterial infections as well as brain tumors such as the cerebellopontine angle tumor. In addition to myopathies and peripheral and central paresis, the lavator labii superioris muscle may be affected by inflammation and trauma.

Inflammations of the muscle usually result in the context of overloading or incorrect loading. In turn, trauma can be the cause of a torn muscle. Although both phenomena may ultimately affect every muscle, they rarely occur on the lavator labii superioris muscle. The reason for this is the low stress of the muscle in everyday life.

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