The Longitudinalis linguæ inferior is a narrow band situated on the under surface of the tongue

Tongue

The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...

 between the Genioglossus

Genioglossus

The genioglossus is a muscle of the human body which runs from the chin to the tongue. The genioglossus is the major muscle responsible for protruding the tongue.-Structure:...

 and Hyoglossus

Hyoglossus

The Hyoglossus, thin and quadrilateral, arises from the side of the body and from the whole length of the greater cornu of the hyoid bone, and passes almost vertically upward to enter the side of the tongue, between the Styloglossus and Longitudinalis inferior....

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Course

It extends from the root to the apex of the tongue: behind, some of its fibers are connected with the body of the hyoid bone

Hyoid bone

The hyoid bone is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. At rest, it lies at the level of the base of the mandible in the front and the third cervical vertebra behind.Unlike other bones, the hyoid is only distantly...

; in front it blends with the fibers of the Styloglossus

Styloglossus

The Styloglossus, the shortest and smallest of the three styloid muscles, arises from the anterior and lateral surfaces of the styloid process, near its apex, and from the stylomandibular ligament....

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Movement of material through the GI tract is dependent upon the coordinated activity of the longitudinal and smooth muscle of the gut.