The tongue is a remarkable and dynamic organ with a wide range of functions crucial for daily life. It plays a central role in articulating speech. Beyond communication, the tongue is also fundamental for manipulating food during chewing, initiating swallowing, and detecting tastes. This unique organ operates as a muscular hydrostat, a biological structure primarily composed of muscle fibers without skeletal support, enabling its exceptional flexibility and dexterity.
The Tongue’s Muscular Structure
The human tongue is composed of eight paired muscles, totaling 16 individual muscles. These muscles are categorized into two main groups: intrinsic and extrinsic. Intrinsic muscles are located entirely within the tongue’s structure, allowing it to change shape.
Extrinsic muscles originate outside the tongue and insert into it, altering the tongue’s position within the oral cavity. The separation of these muscle groups by fibrous tissue, such as the median septum, facilitates their independent yet coordinated actions. This dual system provides the tongue with its extensive range of motion and ability to undergo complex shape changes.
Intrinsic Muscles: Shaping and Movement
Four paired intrinsic muscles are embedded within the tongue, allowing for precise alterations in its form. The superior longitudinal muscle, found along the upper surface, shortens the tongue and curls its tip upward, contributing to dorsiflexion. Conversely, the inferior longitudinal muscle, located along the undersurface, shortens the tongue and curls its tip downward, enabling ventroflexion. Both longitudinal muscles also contribute to widening the tongue.
The transverse muscle fibers extend horizontally from the median fibrous septum to the lateral margins of the tongue. Contraction of these muscles narrows and elongates the tongue. The vertical muscle fibers run from the upper surface to the lower surface of the tongue, and their contraction serves to flatten and broaden the tongue. These movements are crucial for shaping the tongue during speech articulation and for manipulating food within the mouth.
Extrinsic Muscles: Positioning and Anchoring
Four paired extrinsic muscles connect the tongue to surrounding bony structures, enabling its gross movements and positioning. The genioglossus muscle originates from the mental spine of the mandible, located behind the chin, and inserts along the entire length of the tongue and the hyoid bone. This muscle is primarily responsible for protruding the tongue forward and depressing it.
The hyoglossus muscle arises from the body and greater horn of the hyoid bone, then inserts into the lateral aspects of the tongue. Its function is to depress and retract the tongue.
The styloglossus muscle originates from the styloid process of the temporal bone and the stylomandibular ligament, inserting into the posterolateral tongue. This muscle retracts the tongue and elevates its lateral margins.
The palatoglossus muscle originates from the palatine aponeurosis of the soft palate and inserts into the lateral aspect of the tongue. This muscle elevates the posterior part of the tongue, helps close the oropharyngeal isthmus, and assists in initiating swallowing. Notably, the palatoglossus is the only tongue muscle not innervated by the hypoglossal nerve, instead receiving innervation from the vagus nerve.