How the Tongue Works: Anatomy, Functions, and Student FAQs
The tongue is a muscular organ that is present on the floor of the mouth. It is devoid of any bone and its main purpose is to assist in the process of mastication and it helps in the swallowing of the food. The tongue is the second organ after teeth that initiates the process of digestion. It is the organ required for perceiving a variety of tastes and also helps in the process of speech. The upper portion of the tongue comprises taste buds that are submerged within Lingual Papillae. The texture of the Tongue is typically rough because of the Lingual Papillae. These are small round structures present upon the upper surface of the tongue. This portion of the tongue is extremely sensitive due to the rich supply of nerves and blood vessels and is always kept moist by the saliva.
Structure of The Tongue
In Humans, the tongue is divided into two parts, the front part that is the oral part which is about two-thirds of the total length of the tongue responsible for the perception of taste, and the posterior part that is also called as the pharyngeal part which is the base of the tongue that lies close to the throat. This is nearly one-third of the total length of the tongue. The anterior portion of the tongue is the tip of the tongue and is narrow and thin followed by the thicker and broader part that lies behind. The posterior part of the tongue is connected to the Hyoid bone. The average length of the tongue is about 8-10 cm. The left and right portion of the Tongue is also divided by a fibrous tissue that lies vertically and ends into a groove and median sulcus on the surface.
The Tongue comprises of a group of intrinsic muscles which are 4 in number that helps in the altering of the shape of the tongue and are not attached to the bone and a group of extrinsic muscle that are 4 in number and are paired, these are attached to the bone and helps in the movement of the Tongue by changing the position of the Tongue. The tongue is further divided into anterior and posterior parts by a V-shaped groove known as the Terminal Sulcus. The Foramen Cecum is a blind foramen that lies at the tip of the terminal sulcus. This is formed during early embryonic development and is the leftover of the Thyroid Diverticulum.
Coming to the upper surface of the tongue which is called Dorsum of the tongue. The Dorsum of the tongue is divided into two halves by a median sulcus. The end of this division is marked by the foramen cecum. The nerves that supply the pharyngeal part and the oral part are Glossopharyngeal nerves and Lingual nerves respectively.
The lower surface of the tongue comprises of Frenulum. This is a fold of mucous membrane that lies in between the tongue at the lower surface that binds the tongue to the floor of the mouth. Both the sides of the frenulum consists of sublingual caruncles in which the saliva from the submandibular glands drain into. The submandibular glands make 70% of the saliva whereas the parotid gland and sublingual gland make 25% and 5% of saliva respectively.
The extrinsic muscles of the tongue are namely:
Genioglossus
Hyoglossus
Styloglossus
Palatoglossus
These muscles help the tongue move from side to side and to protrude and retract as well.
The intrinsic muscles are:
Superior longitudinal muscles
Inferior longitudinal muscles
Vertical muscle
Transverse muscle
These muscles help in shaping the tongue and help in swallowing of food and liquid, they also help in assisting the speech mechanism.
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Tastes Perceived By The Tongue
The tongue is said to identify 4 types of tastes that are: sweet, salty, bitter, and sour. The taste perception in the mouth depends upon the quantity and also on the level of identity of the stimuli. The intensity of the perception of taste depends upon the concentration of the stimulus. The body responds to different tastes and promotes more intake of the content that has enough concentration of carbohydrates and salts since the taste cells of the tongue respond more to these essential substances. Because of this reflex activity, the taste cells tend to identify substances that are bitter and are poisonous to the body even if they are ingested in low concentrations. As the sensitivity towards taste and hearing progresses with age, the need for the concentration of spices increases in adults when compared to children.
The arrangement of taste perception on different locations of the tongue was first proposed in the year 1901 by Dieter Hanig. According to his theory, the sweet taste is identified over the tip of the tongue, salt over the posterolateral edges, sour on the medial lateral edges, and finally bitter on the back of the tongue. This does not mean the other parts of the tongue cannot perceive the taste but it rather means these portions of the tongue are more sensitive to taste than the rest of the areas of the tongue. Different locations on the tongue hold different threshold levels for taste perception. Among all the tip of the tongue is considered to be most sensitive. Though the perception of the bitter-tasting compounds is more towards the back of the tongue practically.
The theory that states tongue is capable of perceiving only 4 main tastes that are sweet, salt, bitter, and sour is practically untrue since individuals also perceive a variety of other tastes than the above-stated ones which also includes pungent taste, astringent taste, metallic taste, and fatty taste which proves how sensitive the taste buds of the tongue are.
Development of Tongue During Embryonic Stage
The tongue starts developing during the fourth week of Embryonic Development. It begins developing as the median bud of the tongue from the first pharyngeal arch. The fifth week leads to the development of the lateral lingual swellings on both sides of the first pharyngeal arch. These swellings very soon swell and cover the median tongue bud. Then the anterior part of the tongue is formed which is the two-third of the total length of the tongue. This continues to develop in the further weeks of prenatal development. Median sulcus marks the line of the fusion.
Blood and Nerve Supply
Lingual artery and a branch of the external carotid artery supply blood to the tongue. Even the blood supply to the floor of the tongue is supplied by the Lingual artery. However, there is also a secondary blood supply to the tongue which is done by the ascending pharyngeal artery and the tonsillar branch of the facial artery.
The nerve supply is classified into special sensory fibers responsible for taste, general sensory fibers responsible for sensation in the tongue, and motor fibers supply.
The motor nerve supply to all the muscles of the tongue takes place by the efferent motor nerve fibers typically by the hypoglossal nerve except the palatoglossus and supplied by the vagus nerve.
The different parts of the tongue drain into different nodes. The tip of the tongue drains into the submental node. Posterior one-third of the tongue drains into jugulo-omohyoid nodes and the anterior two-thirds of the tongue drain into submandibular lymph nodes.
Function of The Tongue
The presence of Tastants help in the understanding of the sense of taste. These are the chemical molecules that mix with the ingested food or saliva and activate the taste receptor cells. The taste receptor cells are present within the taste buds and the dorsal surface of the tongue has numerous taste buds. The different varieties of taste are detected and differentiated by the different taste receptor cells.
The tongue is one of the accessory organs of the digestive system. It assists in the process of mastication by getting the food between the teeth and the hard palate. It also helps in swallowing of the masticated food. The tongue also helps the process of speech. The muscles in the tongue are responsible for giving various shapes to the tongue that in turn facilitates the speech in an individual.
Diseases of The Tongue
Some of the symptoms that appear on the tongue include:
Pain in the tongue
Swelling of the tongue
Burning sensation on the tongue
Loss of taste either partially or complete
Difficulty in the movement of the tongue
These symptoms either appear independently or in association with other diseases such as:
Thrush: The growth of yeast over the surface of the tongue and mouth. This generally happens in individuals who are exposed more to steroids.
Atrophic Glossitis: The rough surface of the tongue turns to become smooth. This usually happens with the deficiency of Vitamin B and also in cases of Anemia.
Ulcers: These are also called as Canker Sores. These are the ulcers that appear in the mouth and on the tongue. They don’t have any specific cause and are not contagious.
Oral Cancer: This is a non-healing ulcer that grows over the tongue or any part of the oral cavity. It grows steadily.
Stomatitis: Redness in the oral cavity with burning sensation with the intake of spicy food.
Lichen Planus: This is a kind of condition which is said to be a result of the immune system attacking the skin and altering the lining of the mouth.
FAQs on Tongue Facts: Structure, Functions, and Common Diseases
1. What are the main functions of the human tongue?
The human tongue is a versatile organ with several critical functions. Its primary roles include:
- Mastication: Helping to chew by manipulating food within the mouth.
- Deglutition: Assisting in swallowing by forming food into a soft mass called a bolus and pushing it to the back of the throat.
- Gustation (Taste): Detecting flavours through thousands of taste buds located on its surface.
- Speech: Working with the lips and teeth to articulate sounds, which is essential for forming words.
- Oral Hygiene: Helping to clean the mouth by dislodging food particles from the teeth and gums.
2. What is the average length of a human tongue?
The average length of an adult human tongue, measured from the oropharynx (back of the throat) to the tip, is approximately 10 centimetres (about 4 inches). On average, an adult male's tongue is slightly longer than an adult female's tongue.
3. How do we taste different flavours with our tongue?
We taste flavours using specialised sensory organs called taste buds, which are housed in small bumps on the tongue known as papillae. When food molecules dissolved in saliva come into contact with the taste buds, they send signals to the brain. The brain then interprets these signals as one of the five basic tastes: sweet, sour, salty, bitter, and umami (savory).
4. Is it true that every person has a unique tongue print?
Yes, this is a fascinating fact. Much like a fingerprint, every individual has a unique tongue print. The specific shape of the tongue, along with the unique texture and pattern of its papillae, creates a distinctive print. This has been explored as a potential method for biometric identification due to its uniqueness and difficulty to forge.
5. Why is the tongue considered a unique muscle in the human body?
The tongue is unique because it is a muscular hydrostat. This means it is composed of a complex arrangement of intrinsic and extrinsic muscles but has no internal bone or cartilage for support. This structure allows it to change its shape and position with incredible flexibility and precision, a feature only seen in structures like an elephant's trunk or an octopus's tentacles.
6. How can the tongue's appearance indicate our overall health?
The tongue can act as a diagnostic window to our internal health. A healthy tongue is typically pink and covered with small papillae. Deviations from this can signal potential health issues. For example, a bright red tongue might indicate a folic acid or B12 deficiency, a white coating could suggest oral thrush or poor hygiene, and a pale tongue might be a sign of anaemia.
7. Is the tongue really the strongest muscle in the body?
This is a common misconception. While the tongue is incredibly strong for its size and is one of the most tireless muscles, it is not the absolute strongest. The title of 'strongest muscle' is complex and depends on the metric used (e.g., force, pressure, or endurance). For instance, the masseter (jaw muscle) can exert the most pressure, and the gluteus maximus is the largest muscle capable of generating significant force.
8. What are the different types of papillae on the tongue?
The surface of the tongue is covered with four types of papillae:
- Filiform Papillae: The most numerous type, they are cone-shaped and create the tongue's rough texture. They primarily provide friction for manipulating food and do not contain taste buds.
- Fungiform Papillae: Mushroom-shaped papillae scattered across the tongue's surface, more concentrated at the tip and sides. They contain taste buds.
- Circumvallate Papillae: Large, circular papillae arranged in a V-shape at the back of the tongue. They are few in number but contain many taste buds.
- Foliate Papillae: Located in small folds on the sides of the tongue, these also contain taste buds.
9. How do the tongue and saliva work together during digestion?
The tongue and saliva have a crucial synergistic relationship in the initial stages of digestion. The tongue mechanically breaks down food and manipulates it, while the salivary glands secrete saliva. The tongue then thoroughly mixes the food with saliva, which contains the enzyme salivary amylase to begin the chemical breakdown of carbohydrates. This mixture is formed into a slippery bolus by the tongue, making it easy to swallow.
