Genioglossus Muscle: Structure, Function & Diseases

The genioglossus muscle is the chin-tongue muscle and its function is to extend the tongue forward or out. It participates in sucking, chewing, swallowing, and speaking. The genioglossus muscle also holds the tongue in the oral cavity and prevents it from sliding in front of the trachea.

What is the genioglossus muscle?

As the chin-tongue muscle, the genioglossus muscle stretches from the lower jaw to the tongue. It forms an external tongue muscle; this group is distinguished by the fact that they attach to or originate at the tongue. In contrast, anatomy refers to those muscles that lie on or in the tongue as internal tongue muscles. The tongue has numerous functions: When chewing, it pushes food from the center of the oral cavity to the sides, where the teeth are located. It then carries the food pulp toward the pharynx, where the pharyngeal muscles push the food further toward the esophagus. Meanwhile, other muscles close the airways and ensure that food and liquids enter the stomach. In addition, the tongue plays an important role in articulating sounds and thus in speaking and singing. Humans naturally live in groups and therefore depend on communication. Some experts even assume that the communication abilities of humans are the key to their biological and technological evolution. The brain controls the complex interaction of the various tongue muscles.

Anatomy and structure

The paired genioglossus muscle originates at the spina mentalis of the lower jaw (mandible). There, two projections of different sizes are located: the spina mentalis inferior and the spina mentalis superior. The latter serves as the origin of the genioglossus muscle. From the lower jaw, the striated muscle extends to the tongue, spreading like a fan. Its insertion is distributed over the tongue: some fibers attach in the region of the lingual aponeurosis (aponeurosis linguae), which is a layer of connective tissue. Other fibers of the chin-tongue muscle make use of the hyoid bone (Os hyoideum) as an attachment. The upper hyoid muscles (suprahyoid muscles) and some lower hyoid muscles (infrahyoid muscles) also terminate there. In contrast to these, the medial pharyngeus (constrictor pharyngeus medius) muscle, the chondroglossus muscle, and the hyoglossus muscle originate at the hyoid bone. The remaining fibers of the genioglossus muscle attach to the epiglottis, which closes the larynx during swallowing and protects against the ingress of fluid and food pulp. Anatomy classifies the genioglossus muscle as one of the external tongue muscles. The hypoglossal nerve (“hypoglossal nerve”), which corresponds to the twelfth cranial nerve, is responsible for the nervous supply of the fan-shaped skeletal muscle.

Function and tasks

The genioglossus muscle has the task of pulling the tongue forward or sticking it out. In addition, it pulls the tongue downward. Both movements participate in different processes. During sucking, chewing and swallowing, the genioglossus muscle plays a supporting role. During chewing and after swallowing, the genioglossus muscle corrects the position of the tongue and, together with other tongue muscles, keeps it in the center of the mouth. In this way, the chin-tongue muscle prevents the tongue from sliding backward into the pharynx and overlying the trachea and esophagus. In such a case, the affected person would not be able to breathe. The brain controls the act of swallowing and ensures that all muscles work in coordination with each other. In the central nervous system, the swallowing center does not form an anatomically definable structure; instead, it is a functional unit distributed over several parts of the brain. Most brain areas relevant to swallowing are located in the brainstem. The genioglossus muscle also participates in the formation of sounds and thus in speech production. Tongue sounds represent a special category of sounds whose articulation depends on the muscular structure in the mouth. Tongue sounds are also known as linguals and consist of the tongue-R, S, Sh, and Z.

Diseases

When a healthy person is asleep and awake at rest, the genioglossus muscle is not completely relaxed, but prevents the tongue from covering the trachea. Medical professionals refer to this as obstruction of the airway when it is blocked.Under certain conditions, however, the chin-tongue muscle can no longer perform this task – for example, in the case of unconsciousness or during an epileptic seizure. For this reason, first responders place unconscious persons in the recovery position. In this position, gravity pulls the tongue slightly forward rather than backward into the throat. Epileptic seizures are also often accompanied by visible muscle contractions. If the genioglossus muscle unintentionally stretches the tongue forward in the process, there is a risk that the affected person will bite himself. The genioglossus muscle receives its nerve signals from the hypoglossal nerve. Hypoglossal palsy therefore usually affects the chin-tongue muscle as well. A characteristic symptom of hypoglossal nerve palsy is seen when the tongue hangs down to one side when sticking out. The symptom may show up, for example, after a stroke in which a circulatory disturbance compromises the supply of oxygen to the brain. Without oxygen from arterial blood, nerve cells die and resulting damage can be irreversible. However, paralysis of the hypoglossal nerve is not always due to a stroke. When the genioglossus muscle becomes flaccid due to nerve palsy, swallowing and speech problems are possible.