Tongue: Definition, Structure, Anatomy, Muscles & Function

Structure of Tongue Overview

The tongue is a remarkable organ that plays a crucial role in various essential functions, including chewing, swallowing, speaking, and gustatory perception. Understanding the structure and function of the tongue is key to appreciating its significance in our daily lives. In this comprehensive guide, we will delve into the intricate details of the tongue, its parts, and its functions.

What is a Tongue?

The tongue, situated in the mouth, is a muscular organ covered by wet, pink tissue known as mucosa. Its rough texture is attributed to small bumps called papillae, on which thousands of taste buds are distributed. These taste buds consist of nerve-like cells that connect to nerves leading to the brain. The tongue is supported by strong tissue and mucosa, with the front being held by a thread-like structure called the frenum. Additionally, the tongue is connected to the hyoid bone at the back of the mouth.

1. The tongue plays a vital role in essential functions such as chewing, swallowing, and speech. It also plays a significant role in the perception of taste, with sweet, sour, bitter, and salty being the four primary flavors that can be detected.
2. When the tongue encounters glutamate, an additional flavor called umami (found in MSG) can be sensed.
3. With its abundance of nerves, the tongue assists in the detection and transmission of taste information to the brain. Consequently, all areas of the tongue are capable of perceiving these four fundamental flavors.

Structure of Tongue: Anatomy

The tongue is a muscular organ located within the oral cavity. It is primarily composed of muscles, glands, and mucosa. On average, the length of the tongue ranges from 10 to 15 centimeters, with some individual variation. Let's explore the different parts of the tongue in detail.

1.Tip of the Tongue

The tip of the tongue, also known as the apex, is the most mobile part of the organ. It is responsible for the precise movements required for various functions, such as articulating sounds during speech and manipulating food during chewing.

2.Body of the Tongue

The body of the tongue forms the majority of its mass. It extends posteriorly from the tip to the root. The dorsal surface of the tongue is covered with specialized structures called papillae, which give the tongue its rough texture. These papillae house the taste buds, which play a vital role in gustatory perception.

3.Base of the Tongue

The base of the tongue is situated at the posterior part of the organ. It is connected to the hyoid bone and serves as the anterior wall of the oropharynx. Unlike the rest of the tongue, the base does not contain lingual papillae. Instead, it is populated by lymphatic tissue known as lingual tonsils.

4.Papillae and Taste Buds

The dorsal surface of the tongue is covered with various types of papillae, each with its unique characteristics. These papillae house the taste buds, which are collections of nerve-like cells that relay taste signals to the brain.

• Filiform Papillae: These thread-like papillae are located on the anterior two-thirds of the tongue. Unlike other papillae, filiform papillae do not contain taste buds. They primarily contribute to the tongue's rough texture.
• Fungiform Papillae: Mushroom-shaped fungiform papillae are distributed mainly on the sides and tip of the tongue. They contain approximately 1,600 taste buds and are involved in detecting different tastes.
• Circumvallate Papillae: Situated at the back of the tongue, circumvallate papillae are larger and fewer in number compared to other papillae. They contain approximately 250 taste buds and play a crucial role in taste perception.
• Foliate Papillae: These papillae are found on the lateral surface of the tongue as vertical folds of tissue. They are involved in taste perception and contribute to the tongue's overall texture.

5.Muscles of the Tongue

The tongue is predominantly composed of muscles, which allow for its wide range of movements. There are both intrinsic and extrinsic muscles responsible for the tongue's versatility.

• Intrinsic Muscles: Four pairs of intrinsic muscles enable the tongue to change shape and perform intricate movements. These muscles include the superior longitudinal muscles, inferior longitudinal muscles, transverse muscles, and vertical muscles.
• Extrinsic Muscles: The tongue is also influenced by various extrinsic muscles that originate outside the organ and insert into it. These muscles include the palatoglossus, styloglossus, hyoglossus, genioglossus, and geniohyoid. They contribute to actions such as swallowing, tongue elevation, and tongue depression.

Structure of Tongue

The tongue is a muscular organ located in the mouth. It is composed of several key structures that contribute to its overall structure and function.

Muscles

The tongue contains intrinsic and extrinsic muscles that allow it to move in various directions. The intrinsic muscles are responsible for shaping the tongue during speech and swallowing, while the extrinsic muscles enable broader movements such as protrusion, retraction, and side-to-side motions.

Mucosa

The surface of the tongue is covered by a moist and pink tissue called mucosa. It provides protection and lubrication for the tongue. The mucosa contains numerous tiny projections called papillae, which give the tongue its rough texture.

Papillae

Papillae are small bumps found on the surface of the tongue. They contain taste buds and provide sensory perception of taste. There are different types of papillae, including fungiform papillae (scattered throughout the tongue), foliate papillae (located on the sides of the tongue), circumvallate papillae (larger papillae located towards the back of the tongue), and filiform papillae (thin, thread-like papillae without taste buds).

Taste Buds

Taste buds are specialized clusters of cells located on the surfaces of papillae. They contain taste receptor cells, which are responsible for detecting different flavors: sweet, sour, bitter, salty, and umami (savory). When these taste receptor cells are stimulated by food or liquids, they send signals to the brain via nerves, allowing us to perceive taste.

Frenum

The frenum is a small fold of tissue that connects the undersurface of the tongue to the floor of the mouth. It helps anchor and stabilize the tongue, especially at the front part.

Hyoid Bone

The hyoid bone is a U-shaped bone located at the base of the tongue, near the back of the mouth. It provides support and attachment for various muscles involved in tongue movement and swallowing.

Overall, the structure of the tongue, with its muscles, mucosa, papillae, taste buds, frenum, and connection to the hyoid bone, allows it to perform essential functions such as chewing, swallowing, speech, and the perception of taste.

 Parts of Tongue

The majority of tongues measure approximately 10 cm in length and can be divided into two distinct parts:

1. Apex or Tip: This is the most mobile part of the tongue. It refers to the front portion of the tongue and is characterized by its pointed shape.
2. Dorsal Surface:The dorsal surface of the tongue is rough and textured. It contains lingual papillae, which are small bumps on the surface, and taste buds, which are responsible for our sense of taste.

The ventral surface of the tongue, which is smooth, is attached to the floor of the oral cavity.

Structurally and developmentally, the tongue can be divided into two parts:

Anterior Two-Thirds

This includes the apex and body of the tongue, extending towards the palatoglossal arch in an oblique direction from the foramen cecum. The dorsal surface of the anterior two-thirds consists of different types of papillae:

• Vallate papillae: Arranged in a V-shape anterior to the sulcus terminalis (a groove on the surface of the tongue) and containing numerous taste buds. Innervation is provided by the glossopharyngeal nerve.
• Fungiform papillae:Mushroom-shaped papillae with red-colored domes, found on the sides and apex of the tongue.
• Filiform papillae: Slender, cone-shaped projections that are aligned in rows parallel to the sulcus terminalis.
• Foliate papillae: These are vestigial and rarely found in humans.

Posterior One-Third

This portion constitutes the base of the tongue and is located behind the palatoglossal folds. It serves as the anterior wall of the oropharynx. Unlike the anterior two-thirds, the posterior one-third does not have lingual papillae. Instead, the mucosa is populated by lymphatic tissue called lingual tonsils.

In summary, the tongue is divided into the anterior two-thirds and the posterior one-third. The anterior part includes the tip and body of the tongue, featuring various types of papillae on its dorsal surface. The posterior part consists of the base of the tongue and lacks lingual papillae, being characterized by the presence of lingual tonsils.

Area Below the Tongue

1. Beneath your tongue lies a curved area of tissue called the floor of the mouth. This smooth region of soft tissue is connected to the underside of the tongue by a distinct fold of tissue known as the lingual frenulum.
2. The lingual frenulum is a fold of mucous membrane located underneath the central part of the tongue. By lifting your tongue and looking in the mirror, you can observe it. The lingual frenulum plays a role in securing the tongue within the oral cavity.
3. Adjacent to the frenulum, there are small, raised areas called sublingual caruncles.

Structure of Tongue: Muscle Functions

Muscles typically serve the purpose of connecting one bone to another through tendons. However, the tongue is a unique structure that consists of a boneless mass capable of various movements such as protrusion, folding, inversion, laying flat, or filling the mouth as desired. The muscles of the tongue can be classified into two types: intrinsic muscles and extrinsic muscles.

Intrinsic Muscles 

The tongue's intrinsic muscles include the superior longitudinal, inferior longitudinal, transverse, and vertical muscles, all of which are paired. These muscles are connected to different regions of the tongue and play a role in shaping and sizing it. The intrinsic muscles of the tongue receive motor innervation from the hypoglossal nerve. Here is a further explanation of their functions:

1. Superior longitudinal muscle:This muscle curls the tip and sides of the tongue upward while shortening its length.
2. Inferior longitudinal muscle: It curls the tip of the tongue downward and also shortens the tongue.
3. Transverse muscle: This muscle narrows and elongates the tongue, increasing its height and causing it to protrude.
4. Vertical muscle:It flattens and broadens the tongue within the mouth, resulting in protrusion or pushing against the front teeth.

Extrinsic Muscles

The extrinsic muscles of the tongue are a group of four muscles that originate outside the mouth, in contrast to the intrinsic muscles. They are entirely contained within the tongue and do not have any external attachments. These muscles primarily contribute to repositioning the tongue, while the intrinsic muscles alter its shape. The four extrinsic tongue muscles are described as follows:

1. Genioglossus: This large, fan-shaped muscle constitutes the majority of the tongue's mass. It lowers the tongue and can pull it forward, causing protrusion or even sideways movement.
2. Hyoglossus:A slender, four-sided muscle that lowers and retracts the tongue back into the mouth.
3. Styloglossus:Although it is a small muscle, it contains fibers that connect to the hyoglossus muscle. It is responsible for retracting and elevating the tongue, creating a trough-like shape to facilitate swallowing food.
4. Palatoglossus:This muscle is part of the soft palate rather than the tongue itself. Its function is to elevate the posterior section of the tongue.

In summary, the tongue's structure involves a combination of intrinsic and extrinsic muscles, each serving distinct roles in shaping, positioning, and facilitating its movements for functions such as speech, swallowing, and oral manipulation.

Functions of the Tongue

The tongue serves multiple essential functions in our daily lives. Let's explore these functions in detail:

Mastication

One of the primary functions of the tongue is to aid in the process of mastication or chewing. The tongue helps move food around the mouth, mixing it with saliva and breaking it down into smaller, more manageable pieces.

Deglutition

Deglutition, or swallowing, is facilitated by coordinated movements of the tongue. The tongue helps propel the chewed food to the back of the throat, initiating the swallowing reflex and allowing the food to pass into the esophagus.

Taste Perception

The tongue is intricately involved in taste perception. The taste buds on the surface of the papillae detect the presence of different tastes, including sweet, salty, sour, bitter, and umami. These taste signals are then transmitted to the brain, allowing us to savor and differentiate various flavors.

Speech Articulation

The tongue plays a crucial role in speech articulation. It works in conjunction with other oral structures to produce a wide range of sounds and facilitate clear communication. The precise movements and positioning of the tongue contribute to the formation of different speech sounds.

Secretion of Saliva

Saliva plays a vital role in maintaining oral health and facilitating digestion. The tongue contributes to saliva production by secreting mucous and serous fluids. These fluids help keep the mouth moist, aid in food digestion, and protect the oral tissues.

Salivary Glands and their Role

The tongue's functions are supported by the secretion of saliva, which is produced by the salivary glands. There are three pairs of major salivary glands that contribute to saliva production:

• Parotid Glands: The parotid glands are the largest salivary glands located on the inner surface of the cheeks. They release saliva into the oral cavity through Stensen's duct.
• Submandibular Glands:The submandibular glands are located beneath the lower jaw. They secrete saliva into the oral cavity through Wharton's duct.
• Sublingual Glands:The sublingual glands are situated below the tongue. They release saliva into the oral cavity through multiple ducts known as the ducts of Rivinus.

These salivary glands play a crucial role in maintaining oral hygiene, lubricating the oral cavity, and aiding in the digestion of food.

Types of Papillae

Papillae are small, raised structures found on the surface of the tongue. They provide texture and contribute to various functions of the tongue, such as taste perception, manipulation of food, and aiding in speech articulation. Papillae can vary in size, shape, and distribution across the tongue. There are several types of papillae, including filiform, fungiform, circumvallate (or vallate), and foliate papillae. These papillae may differ in their appearance, location on the tongue, and presence of taste buds. Together with taste buds, papillae play a crucial role in our sense of taste by detecting and relaying information about different flavors to the brain.

There are four main types of papillae on the surface of the tongue:

1. Filiform Papillae:These are the most numerous and have a slender, thread-like shape. They cover the anterior two-thirds of the tongue's dorsal surface and do not contain taste buds. Filiform papillae aid in the manipulation of food and contribute to the tongue's rough texture.
2. Fungiform Papillae: These papillae are mushroom-shaped and scattered among the filiform papillae. They are more prominent on the sides and tip of the tongue. Fungiform papillae contain taste buds and play a role in taste perception.
3. Circumvallate (Vallate) Papillae: These papillae are large, circular-shaped structures located at the back of the tongue in a V-shaped row. They have a trench-like groove surrounding them. Circumvallate papillae house numerous taste buds and contribute to the detection of taste.
4. Foliate Papillae: These papillae are present on the lateral edges of the posterior part of the tongue. They are ridged or leaf-like in appearance. Foliate papillae contain taste buds, although they may be less developed or absent in some individuals.

These papillae, along with taste buds located on their surfaces, are responsible for our sense of taste and contribute to the overall texture and function of the tongue.

Additional Information: The sense of taste is intimately connected to our sense of smell. The combination of taste and smell allows us to experience the full spectrum of flavors in our food and beverages.

Structure Of Tongue: Things to Remember

1. Positioned within the mouth, the tongue is a muscular organ.
2. The presence of papillae, small bumps, gives the tongue its rough texture.
3. The surfaces of the papillae are covered with numerous taste buds.
4. The tongue is indispensable for chewing, swallowing, and speech production. It enables us to perceive the four primary taste sensations: sweet, sour, bitter, and salty.
5. The tongue contains a rich network of nerves that play a crucial role in detecting and transmitting taste information to the brain.
6. The central or terminal sulcus holds significant anatomical importance within the tongue.
7. The functions of the tongue encompass speech articulation, eating and swallowing, taste perception, mastication or chewing, and assistance in breathing, among others.