When talking, swallowing, chewing and yawning, the tongue is indispensable. Their movements are based on the interplay of many different muscles, including the internal tongue muscles. One of them is the transversus linguae muscle. It represents a small, striated skeletal muscle and participates mainly in movements in the longitudinal direction of the tongue - for example, when pulling out.
The internal tongue muscles also include the longitudinal inferior muscle and the longitudinal superior muscle, both of which extend longitudinally through the tongue. The verticalis linguae, which extends between the tongue aponeurosis (Aponeurosis linguae) and the back of the tongue, also belongs to the internal tongue muscles. The names are derived from the respective anatomical position of a muscle. Within the tongue, all muscles are interwoven in three dimensions. In addition to the internal tongue muscles, which is an intrinsic musculature of the organ, humans also have an external tongue musculature, which is located outside of the organ.
The transversus linguae muscle runs across the tongue. Its origin is located on the septum (septum linguae), which is located in the middle of the tongue and often forms a middle fold when pulled out. The transversus linguae muscle extends from the septum to the lateral tongue margin.
Unlike other striated muscles, it does not have ordered muscle fiber bundles, each containing multiple muscle fibers. Instead, its fibers pass through the tongue tissue and are intertwined with other fibers. Through each muscle fiber, which corresponds to a muscle cell with multiple cell nuclei, are longitudinally aligned myofibrils. These threads are divided into sections called sarcomeres, which are responsible for the striated structure of the muscle.
Protein structures produce differently translucent parts that appear under the microscope as light and dark bands. These bands are the contractile units of the muscle: they can nest and shorten each other. The signal is given to the transversus linguae muscle from the twelfth cranial nerve (hypoglossal nerve), which anatomy also calls the tongue-throat nerve because of its course.
The transversus linguae muscle is active in various tongue movements: when stretching and sticking out the tongue as well as at the transverse curvature. However, as the transversus linguae muscle is intertwined with the other internal tongue muscles, it is not the only one responsible for the movements.
During the swallowing process, the transversus linguae muscle is mainly involved in the oral preparation phase and the oral transport phase. These two sections represent the first two steps in the act of swallowing. In the oral preparation phase, the mouth chops food between the teeth. The tongue movements have two functions: on the one hand they ensure that the tongue does not accidentally get caught between the teeth, on the other hand they repeatedly push the chyme from the middle of the mouth to the sides. This is where the transverse curvature of the tongue comes into play, for which the transversus linguae muscle is responsible.
If the food is sufficiently chopped or the person only swallows liquid, then follows the oral transport phase. First, the tongue muscles press the tongue to the palate, tilting it backwards so that the food can already slide back to the throat. In addition, the internal tongue muscles cause a wave motion, which supports the transport. In the throat, the contact of the food triggers the swallowing reflex and the pharyngeal transport phase begins: After the nose and larynx or trachea have closed, the muscles push through the throat into the esophagus. There begins the oesophageal transport phase, which ends when the food or fluid enters the stomach.
The transversus linguae muscle is also necessary for speech. The tongue contributes to the articulation of sounds and forms, for example, consonants such as "L" and "N".
In hypoglossal palsy, the nervous system of the transversus linguae muscle is completely or partially interrupted. As a result, symptoms of swallowing, chewing and speaking are evident. The tongue can hang down on one side when pulling out or make an overall flaccid impression.
Often only half of the tongue is affected by hypoglossal paralysis. When the failure of the twelfth cranial nerve is irreversible or long-lasting, the body gradually degrades the affected muscles. In this case, the medicine speaks of an atrophy, that is a tissue loss. Hypoglossal paralysis may be due to damage in the periphery, but may also be due to diseases of the central nervous system. It often occurs as part of an ischemic stroke. Poor blood flow to the brain triggers cerebral infarction and causes neurological symptoms such as confusion, speech disorders, hemiplegia, cognitive impairment, impaired vision or motor difficulties.
However, the symptoms may vary in individual cases as they depend on the location and extent of the affected brain regions. Hypoglossal palsy affects not only the transversus linguae muscle but also the other tongue muscles. In addition, infections, bleeding, craniocerebral trauma, tumors and other diseases may be the cause of hypoglossal nerve palsy. Less frequently, the hypoglossal nerve is damaged during surgical procedures in the head and neck region.Tags: