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The genioglossus is a paired tongue muscle that is in the group of extrinsic muscles of the tongue. The other extrinsic muscles of the tongue are the hyoglossus (chondroglossus), styloglossus, and the palatoglossus.[1][1] All of these extrinsic muscles are within proximity of one another, which is why the entirety of the extrinsic muscle group usually functions as a unit. Each muscle has its individual function, but there tends to be more than one extrinsic muscle functioning at the same time. Histologically, the genioglossus muscle has significant type 2 fibers present in the anterior section of the genioglossus muscle, whereas the posterior portion of the muscles does not have a large portion of type 2 fibers present. The specific fibers present in the particular portion of the genioglossus muscle determine the function of the muscle. For example, the anterior portion of the genioglossus contains type 2 fibers, and this suggests that this portion of the genioglossus muscle participates in phasic action.[2] The posterior portion, while it does not contain many type 2 fibers, has significant muscle strength compared to the anterior portion of the genioglossus; because of this, there are suggestions that the posterior portion of the genioglossus holds responsibility in the nasopharyngeal airway, as well as in the production of the sound of vowels.[2][3][4]