Tongue

The Tongue is an organ that plays a crucial role in both the digestive process and speech production. It is an accessory digestive organ made up of skeletal muscles covered with a mucous membrane. Situated in the oral cavity, the tongue, along with its associated muscles, forms the floor of the mouth. Divided into symmetrical lateral halves by a median septum, the tongue is attached to the hyoid bone, styloid process of the temporal bone, and mandible, giving it stability and mobility.

Musculature of tongue

The tongue’s movement and manipulation are made possible by its extrinsic and intrinsic muscles.

1. The extrinsic muscles, originating outside the tongue and inserted into connective tissues within it, include the hyoglossus, genioglossus, and styloglossus muscles. These muscles allow the tongue to move side to side and in and out, assisting in chewing, shaping food into a rounded mass, and pushing it to the back of the mouth for swallowing. Additionally, they form the floor of the mouth and maintain the tongue’s position.
2. The intrinsic muscles of the tongue originate and insert into connective tissues within the tongue itself. These muscles contribute to altering the tongue’s shape and size, essential for speech and swallowing. Some intrinsic muscles include the longitudinalis superior, longitudinalis inferior, transversus linguae, and verticalis linguae muscles, each playing a specific role in tongue movement.

Lingual frenulum

It is a fold of mucous membrane found on the undersurface of the tongue, that connects the tongue to the floor of the mouth. It serves to limit the tongue’s posterior movement. When a person has an abnormally short or rigid lingual frenulum, a condition known as ankyloglossia or being “tongue-tied,” speech can be impaired. However, this condition can be surgically corrected.

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Lingual papillae

The upper surface and sides of the tongue are covered with papillae, nipple-shaped projections formed by the lamina propria covered with stratified squamous epithelium.

1. Filiform papillae are the most numerous and cover most of the tongue’s dorsal surface. They are slender, thread-like papillae and do not contain taste buds. Instead, their primary function is to increase friction between the tongue and food, aiding in the manipulation of food during chewing and swallowing.
2. Fungiform papillae are mushroom-shaped papillae that are scattered among the filiform papillae on the tongue’s surface. These papillae contain taste buds and are involved in taste perception. They are particularly sensitive to sweet, sour, and salty tastes.
3. Circumvallate papillae are large, circular papillae located at the back of the tongue in a V-shaped row. They also contain taste buds and are responsible for detecting different tastes. There are typically only a few circumvallate papillae on the tongue, and they are involved in taste perception and the initiation of the swallowing reflex.
4. Foliate papillae are leaf-shaped papillae found on the sides of the tongue, especially in the posterior region. They contain taste buds and play a role in taste perception, particularly for bitter tastes. While they are more prominent in infants and young children, foliate papillae tend to decrease in size and become less visible with age.

Lingual glands

Lingual glands in the lamina propria of the tongue secrete mucus and a watery serous fluid containing the enzyme lingual lipase. This enzyme plays a vital role in the initial digestion of dietary triglycerides, converting them into simpler fatty acids and diglycerides.

Foramen Cecum

The foramen cecum is a small depression or pit-like structure located at the back of the tongue, near the base. It is the region that marks the origin of the thyroid gland during during early fetal development. The foramen cecum is situated at the junction of the anterior two-thirds and the posterior one-third of the tongue.

Lingual tonsils

The lingual tonsil is a part of the lymphatic system located at the base of the tongue. It consists of clusters of lymphoid tissue covered with mucous membranes and plays a vital role in the body’s immune response. Like other tonsils (palatine, tubal, and pharyngeal), it helps protect against infections by detecting and trapping harmful pathogens that may enter through the mouth. The lingual tonsil can become inflamed or enlarged due to infections, causing discomfort and difficulty swallowing. Medical evaluation and treatment may be necessary in such cases.

Functions of the Tongue

• Taste perception

The tongue is renowned for its role in providing our sense of taste, enabling humans to discern five fundamental taste sensations: sweet, salty, bitter, sour, and umami. This gustatory sense aids the brain in determining the nutritional value of what is being consumed. Bitter or sour tastes can signal spoiled food, while salty or sweet tastes indicate high caloric content, aiding in food evaluation.

• Mastication

Scientifically referred to as mastication, chewing involves the breakdown of food with the assistance of saliva. The tongue plays a pivotal role in this process by ensuring proper mixing of food particles and saliva. Thorough chewing enhances nutrient accessibility, facilitates swallowing, and promotes smoother digestion. Functionally, the tongue aids in maneuvering food within the oral cavity, combining it with saliva, and forming it into a cohesive bolus ready for swallowing.

• Deglutition

After thorough mastication and blending with saliva, food transforms into a compact mass termed a bolus. The tongue serves as a propulsive force, guiding the bolus from the oral cavity to the esophagus. Subsequently, the bolus travels through the esophagus to reach the stomach for digestion.

• Articulation and phonation

Analogous to the teeth, the tongue assumes a pivotal role in articulation and sound formation during speech. While speaking, air from the lungs vibrates the vocal cords, and the resulting vibrations travel through the mouth. The tongue, in conjunction with the teeth and lips, shapes the airflow, generating diverse sounds. For instance, critical sounds such as “T,” “D,” and “L” heavily rely on the tongue’s positioning and movement during speech.

Summary

The tongue, a vital organ in the oral cavity, serves essential functions in both the digestive and communication processes. Comprising skeletal muscles covered by mucous membranes, it plays a crucial role in taste perception, detecting sweet, salty, bitter, sour, and umami flavors, aiding the brain in assessing nutritional value and potential hazards of ingested substances. Additionally, the tongue is pivotal in mastication, effectively breaking down food with the assistance of saliva, enhancing nutrient accessibility, and facilitating swallowing.

It propels the compacted bolus to the esophagus for digestion. Furthermore, the tongue is integral to speech formation, collaborating with the teeth and lips to modulate airflow and generate distinct sounds. Its anatomy, including extrinsic and intrinsic muscles, lingual frenulum, lingual papillae, and lingual glands, collectively enables these functions. The lingual tonsil, part of the lymphatic system, contributes to the immune response. Its significance lies not only in its multifaceted roles but also in its potential to reflect overall health and well-being.

FAQs on Tongue

What are the primary taste sensations that the tongue can detect?

The tongue can sense five fundamental taste sensations: sweet, salty, bitter, sour, and umami. These tastes play a crucial role in helping the brain evaluate the nutritional content and safety of the food being consumed.

How does the tongue contribute to the process of chewing?

Chewing, scientifically known as mastication, involves breaking down food with the help of saliva. The tongue plays a key role in this process by ensuring proper mixing of food particles and saliva. Effective chewing enhances nutrient accessibility, aids in swallowing, and promotes efficient digestion.

What is the function of the lingual frenulum?

The lingual frenulum is a fold of mucous membrane located on the undersurface of the tongue, connecting it to the floor of the mouth. It limits the tongue's posterior movement and aids in speech and swallowing. In cases of ankyloglossia, or being tongue-tied, an abnormally short or rigid frenulum can impair speech and may require corrective measures.

How does the tongue play a role in the process of swallowing?

After thorough chewing and mixing with saliva, food forms a bolus. The tongue propels this bolus from the oral cavity to the esophagus, initiating the process of swallowing. The bolus then travels through the esophagus and reaches the stomach for further digestion.

What is the significance of the lingual papillae on the tongue's surface?

The tongue's upper surface and sides are covered with lingual papillae, which are nipple-shaped projections. Different types of papillae, including filiform, fungiform, circumvallate, and foliate papillae, contribute to taste perception and food manipulation during chewing and swallowing.

How does the tongue contribute to speech and sound formation?

Similar to teeth, the tongue is crucial for speech and sound production. As air flows from the lungs and vibrates the vocal cords, the tongue, along with the teeth and lips, shapes the airflow, producing distinct sounds.

What role does the lingual tonsil play in the immune system?

The lingual tonsil, situated at the base of the tongue, is part of the lymphatic system and aids in the body's immune response. Like other tonsils, it helps detect and trap harmful pathogens that may enter through the mouth, contributing to protection against infections.

How does the tongue contribute to taste perception?

Taste buds, located on various types of lingual papillae, play a crucial role in taste perception. These taste buds detect different flavors and send signals to the brain, allowing us to identify sweet, salty, bitter, sour, and umami tastes and make judgments about the food we consume.

Can abnormalities in the lingual frenulum affect speech and swallowing?

Yes, an abnormally short or rigid lingual frenulum, a condition known as ankyloglossia or being tongue-tied, can impact speech and swallowing. Corrective measures, including surgical intervention, may be necessary to address this condition and improve speech and swallowing function.

What is the role of the intrinsic and extrinsic muscles of the tongue?

The extrinsic muscles, which originate outside the tongue, allow for its movement in various directions and contribute to functions like chewing and swallowing. Intrinsic muscles, originating and inserting within the tongue itself, play a role in altering its shape and size, crucial for speech and swallowing.