- Skeletal system
- Blood vessels
- Respiratory system
- Digestive system
- Endocrine glands
- Nervous system
- Lymphatic system
- Female reproductive system
- Male reproductive system
The tongue (Latin: lingua s. glossa) is a pink mobile muscular organ of the digestive system covered by mucosa and located in the oral cavity proper extending to the oropharynx. It helps to support the floor part of the cavity. The tongue not only helps in food chewing and swallowing, but it also provides tactile, taste, and speech formation functions.
The tongue has three parts, two surfaces and two edges. Men’s average tongue length is around 8.5 cm (3.35 inches), while for women it is 8 centimeters (3.15 inches).
The tongue attaches by muscles to the hyoid bone, the styloid process of temporal bone, mandible, palate, and pharynx.
The tip of the tongue faces the teeth and gingiva, as well as the tongue’s anterior lateral sides.
Posterior lateral sides meet the palatoglossal and palatopharyngeal arches and palatine tonsils between them.
Superior from the tongue is the soft and hard palate, while inferior is the oral cavity’s floor and sublingual salivary glands.
Posterior is the epiglottis and oropharyngeal isthmus.
The tongue participates in the oral cavity’s posterior opening formation. It is known as the oropharyngeal isthmus or opening. The tongue’s base and the lingual tonsil demarcate the isthmus from the bottom.
Parts and edges
The tongue consists of three parts- the apex, also known as the tip, body, and root.
The apex is the most mobile and narrowest part, located most forward.
Most of the tongue makes the body part. It continues from the tip’s end to the terminal sulcus located in the tongue’s dorsal surface, approximately two-thirds from the apex.
The tip, together with the body, forms the anterior part. It is also known as the oral or pre-sulcal part.
The posterior part or posterior one-third is the root. It is also known as the postsulcal or pharyngeal part. It starts with the terminal sulcus and ends with the epiglottis. It is the broadest and the least mobile area of the tongue and, in this part, locate lymphoid tissue and tonsil. In its place, it fixes several extrinsic muscles connecting the root with the hyoid bone and mandible.
The tongue has two lateral edges or sides located between both surfaces.
The tongue has two surfaces- the superior and the inferior.
The superior surface is also known as the dorsal, while the inferior is the ventral surface.
Compared to the dorsal surface, the ventral surface is relatively smooth. It is more pronounced at the tip and the anterior part of the tongue’s body areas.
In the midline of the ventral surface, mucosa forms a lingual frenulum connecting the tongue with the oral cavity floor.
The lingual frenulum ends with the minor swelling- sublingual caruncle. It is the part where opens the sublingual salivary gland central duct and submandibular salivary gland duct. From its sides laterally goes sublingual folds or plicas overlying the sublingual glands. On sublingual plicas along the sides and towards the caruncle part opens the sublingual salivary gland’s minor ducts.
Lateral on both sides of the lingual frenulum is the slight fimbriated folds or plicas made from the mucosa. Folds lie next to noticeable lingual veins. Sometimes fimbriated folds’ free edges have small minor bumps, but sometimes they appear with more pronounced processes.
The dorsal surface is convex and curved, faced up and back. The dorsal surface is rough to touch because it contains many lingual papillae. Lingual papillae locate only on anterior two-thirds- till the terminal sulcus.
The terminal sulcus locates on the dorsal surface between the body and the root part. It separates both parts and has an inverse V-shape.
In the middle of terminal sulcus is foramen cecum. In embryonal development, the foramen cecum is the origin of the thyroglossal duct that develops the thyroid gland.
The median lingual sulcus goes in the dorsal surface’s midline from the tip part to the foramen cecum. The median lingual sulcus signifies two lateral lingual swelling fusions in embryological development resulting in tongue formation.
Knowing the median sulcus location makes it easier to determine the median lingual septum location as it goes in the same direction as the sulcus. It is a sagittal oriented connective tissue septum in the midline dividing the tongue into two symmetric parts- the right and left one.
In the root part’s mucosa, locate lingual tonsil, aggregation of lymphoid tissues. Mucosa from the root continues to the epiglottis and results in three mucosal fold formation.
The first one goes from the midline of the tongue’s root up to the epiglottis, and it is called the median glossoepiglottic fold. Two lateral glossoepiglottic folds go from the tongue’s lateral sides up to the sides of the epiglottis. Between the lateral and median folds on both sides forms paired epiglottic vallecula.
The tongue has a connection with the soft palatine’s posterior part. Soft palatine ends with a free edge that forms the uvula in the middle. The anterior part of the uvula’s lateral sides goes to the lateral sides of the tongue’s root, and they are called palatoglossal arches or anterior palatine arches.
Tongue functions as a taste analyzer and, in this part, help lingual papillae. The taste sensation is associated with taste receptor irritation. They locate in unique epithelial structures that resemble buds in shape. They are called taste buds, and they contain sensory receptors.
Tongue’s taste buds are in the lingual papillae’s epithelium. Apex and body parts on the dorsal surface have four lingual papillae groups, divided by their functions and structure. The lingual papillae are wart-like bumps increasing the surface many times.
The tongue has the most significant amount of taste buds. Still, they locate on the throat, epiglottis, nasal cavity surfaces, and in the upper part of the esophagus. Young children also have taste buds on the hard palate, cheeks, and even lips. Every person has around 2000 to 4000 taste buds in total.
Afferent nerves transfer signals from taste buds further to the central nervous system.
This papillae type is thread-like and cone-shaped, thin, and only around 1 millimeter (0.04 inches) in length. They are the only tactile papillae covering almost all anterior two-thirds of the dorsal surface till terminal sulcus. They form rows that go in the anterolateral direction, parallel to the terminal sulcus, but they have a transverse direction in the tip area. It is the most common type making the dorsal surface rough to touch. It has a white and pinkish-grey color, sometimes looking scaly.
The filiform papillae provide the bolus movement further to the oral cavity proper and guide next to the pharynx. They help to clean the teeth and the tongue’s mucosa from the food particles. They also help to perceive the irritation of the external environment.
This type is wider than the filiform papillae. They start with a relatively thin stalk and end with raised termination that contains taste receptors. Because of the shape that looks a little bit like a mushroom, they have a fungiform name. This type is also bigger than filiform papillae. It locates mainly in the tip area and between filiform papillae on the body part. They are very vascular, and they are visible on the tongue as red dots.
The tongue contains around 200-400 fungiform papillae. One fungiform papilla contains approximately 3-6 taste buds, with a maximum of 9 to 18 taste buds. Their height is about 1-2 millimeters (0.04-0.08 inches), but the width is up to 1 millimeter (0.04 inches), the distance between two fungiform papillae is around 2 millimeters (0.08 inches). This type is not only responsible for the taste sensation, but it also contains a small number of sensory cells for temperature and touches.
Foliate papillae are 3-5 millimeters (0.12-0.2 inches) long mucosal folds lying parallel close to each other and separated by grooves on both lateral edges of the tongue close to the terminal sulcus. Every side has around 3-11 papillae. They are very well visible on newborn babies, but over time they become less visible. The mucous membrane covering them contains taste buds.
Circumvallate papillae are also known as vallate papillae. They locate next to the terminal sulcus, they go along it in the pre-sulcal area, forming one line on each side that goes together and has the inverted letter “V” shape. This type is more significant than others. Their height is around 1-3 millimeters (0.04-0.12 inches), but width varies from 0,5 to 2 millimeters (0.02- 0.08 inches). Circumvallate papillae also contain taste receptors. Their count can range from six to fifteen, but usually up to twelve. They don’t rise above the tongue mucosa level, so they can’t get mechanical injuries during food swallowing. Each papilla contains around 150-300 taste buds on its sides. The papilla’s central part looks a little bit like a fungiform papilla as it also has a short stalk ending with broader termination containing taste buds. Still, all around the central part is wrinkle and the mucosal wall, so it looks like the papilla is in the pit. The mucosal fence is higher than the central region. It contains smooth muscle cells that help to hold the nutrients in the wrinkle. Saliva later helps to wash the food particles out of the groove.
The tongue contains skeletal muscles, and all have pairs on the opposite side. All tongue muscles divide into two groups- the intrinsic and extrinsic muscles. Tongue muscle fibers have enormous energy reserves, that is why it does not get tiring.
They start and end in the tongue, attaching to structures located in it.
When these types of muscles contract, the tongue can change its shape and size. All four pairs of muscles go in mutually perpendicular directions naming them. Intrinsic muscles mainly help in speech formation and digestion.
- Superior longitudinal muscles locate close to the dorsal surface. They originate from the root and insert in the tip, running along with the tongue. They shorten it and help to curl the apex and sides upwards. They elevate the tip.
- Inferior longitudinal muscles have better development than superior ones. They locate closer to the ventral surface. They also originate from the root and insert in the tip. They shorten the tongue and curl it downward. They pull the apex down.
- The transverse muscles start from the median lingual septum and insert onto lateral edges. They narrow the tongue by thickening it. They increase its height and protrude it.
- Vertical muscles’ fibers go in the vertical direction connecting both surfaces. They flatten and broaden the tongue.
These type of muscles primarily start from the nearest bones and ends in the tongue. When these muscles contract, they move the tongue. Genioglossus and hyoglossus muscles go below it, while styloglossus and palatoglossus above. Extrinsic muscles primarily help to provide mechanical food and maneuvering functions.
- Genioglossus pulls the tongue forward and down, protruding, extending, and depressing it. Muscles originate in the mandible’s mental spine process and insert in the entire length of the tongue’s dorsal surface and the tongue’s root part, and the hyoid bone’s body.
- Styloglossus pulls the tongue back and up, retracting and elevating it. They start at the temporal bone’s styloid process and end by blending with inferior longitudinal and hyoglossus muscles and inserting in the sides of the tongue and root part.
- Hyoglossus pulls the tongue back and down, depressing and retracting it. They originate from the body and greater horn of the hyoid bone and insert in the root and lateral edges.
- Palatoglossus arises from soft palatine’s aponeurosis, and its fibers insert in the lateral edges and go across the tongue, blending with intrinsic muscle fibers. They elevate the posterior part and close the oropharyngeal isthmus during swallowing.
Tongue muscles cover mucosa with stratified squamous epithelium. Tongue’s mucosa doesn’t have glands. It is immobile and fused with connective tissue located between muscle fibers.
The ventral surface is smooth and doesn’t have keratinization signs. Lingual papillae on the dorsal surface raise above the mucosa except for the circumvallate papillae. Filiform papillae have partially or fully keratinized epithelium. While fungiform papillae epithelium rarely has keratinization signs. Foliate and circumvallate papillae most often have keratinized epithelium partially. In the connective tissue, between muscles locate small salivary glands with openings close to the base of circumvallate and foliate papillae. The tip area has mixed salivary glands but close circumvallate and foliate papillae- serous glands, while in the root of the tongue- mucous salivary glands. Mixed glands in the tip area open on the ventral surface close to the lingual frenulum, while the mucous salivary glands open in the lingual tonsil base.
The tongue has three main functions: mechanical food procession and food maneuvering in the oral cavity, taste, and speech formation, and several minor functions such as providing breathing during sleep and ensuring fast medication absorption by tongue veins when medication applies under the tongue. For example, nitroglycerin dilates the heart’s blood vessels and can be used under the tongue when chest pain is present.
The tongue also has a protector role as it can use to cause vomiting. The posterior third contains nerve fibers from the vagus nerve, and touching them can lead to stomach emptying when ingested undesirable substances.
Food procession and maneuvering
The tongue helps to position food between the teeth and mixes food with saliva, assisting in the mastication process. It also moves the food in the oral cavity, and next to the pharynx, it presses food against the hard palate and helps form a food bolus. The tongue also enables the swallowing process by its movements. It helps to do breastfeeding and sucking. It also helps to clean the teeth and oral cavity’s grooves from the leftover food particles.
The intrinsic muscles help to shape the tongue to provide a speech. Tongue assists in forming the sounds of speech together with lips and teeth. For example, when using the letter “t” and making its sound, the tip touches the alveolar ridge, but when making the letter “g,” the oral tongue’s dorsal surface feels the soft palate.
As written before, the tongue contains various papillae with many taste buds and gustatory cell receptors providing the taste sensation. In total, there are five taste areas. Each is more sensitive to a specific taste, although all the tongue areas can taste all five flavors. The sides of the tongue are more sensitive than the central part.
Salty taste provides a narrow band of the tip area and the lateral edge’s anterior part. The sweet taste area overlays the previous one in the tip area and goes further in the body part. Sour taste provides the posterior part of lateral edges, while bitter- the posterior part of the body area next to the terminal sulcus. The central part of the tongue provides the umami taste. Umami is the savory taste of glutamic acid and glutamate.
The tongue can also be used in general health checkups as changes in color and visual appearance can signal the underlying diseases. For example, the geographic tongue characterizes as discolored and painless patches on the tongue surface with greyish white borders covering the dorsal surface and the edges. Its appearance looks like a map, and the patches usually migrate. It causes inflammation, and the geographic tongue can be a sign of intestine inflammation.
The strawberry tongue appears very red, swollen, and bumpy tongue. Together with other symptoms, it can be a sign of Kawasaki disease or scarlet fever.
The tongue’s arterial supply primarily provides the lingual artery with its branches, such as the dorsal lingual arteries, the sublingual, and the lingual artery’s terminal ending- the deep lingual. The lingual artery is a branch from the external carotid artery.
Tonsillar and ascending palatine arteries from the facial one and ascending pharyngeal artery of the external carotid artery also perfuses the tongue.
The deep lingual veins drain the blood from the ventral surface, while the dorsal lingual veins from the dorsal surface and sides of the tongue.
Together with the sublingual vein, the deep lingual vein forms a vena comitans of the hypoglossal nerve. It drains into the lingual vein. Blood from all mentioned veins carries to the internal jugular vein.
The tongue drains to various lymph nodes via various lymph vessels. The lymphatic drainage can be divided into three regions- the marginal, ventral and dorsal.
The tongue’s anterior parts drain into the marginal and ventral lymph vessels, while the posterior tongue parts into dorsal ones.
The tongue’s tip drains to the same or opposite side’s submental lymph nodes.
The marginal lymph vessels from the anterior two-thirds of the tongue’s lateral sides carry the lymph next to the same side’s submandibular lymph nodes.
The two-thirds of the anterior and more central part of the tongue drains to deep cervical nodes of the opposite side, mainly to jugulodigastric and jugulo omohyoid nodes.
The dorsal vessels carry the same or opposite side’s lymph next to deep cervical lymph nodes, primarily to jugulodigastric and jugulo omohyoid nodes.
Tongue innervation can divide into three general groups- motor, general and special sensory innervation. The last one provides the taste sensation.
The motor innervation
The motor innervation of the tongue primarily provides the hypoglossal nerve (CN XII). It innervates all the tongue muscles, except the palatoglossus muscle. It innervates the vagus nerve (CN X).
The general sensory innervation
The mucosal part of the ventral surface and dorsal surface from the apex to terminal sulcus (anterior two-thirds of the dorsal surface) innervates the lingual nerve from the mandibular nerve. Mandibular nerve is a terminal branch of trigeminal nerve (CN V3).
The posterior two-thirds of the dorsal surface innervates the glossopharyngeal nerve (CN IX).
A small portion of the posterior tongue area innervates the internal laryngeal nerve. It is a branch of the vagus nerve (CN X). Because of the vagus nerve, touching this area can cause vomiting.
The special sensory innervation
Taste sensation provides three nerves.
Fungiform and foliate papillae innervate chorda tympani from intermediate nerve (part of the facial nerve (CN VII)).
Filiform papilla innervates the lingual nerve from the mandibular nerve (trigeminal nerve CN V3).
Circumvallate papillae innervate glossopharyngeal nerve (CN IX).
Changes in tongue color
As mentioned before healthy tongue has a pink color, it is mobile, and the dorsal surface has a rough texture with a thin white coating because of the many papillae. The pink can vary from lighter to darker shade. The most common visible changes affect the tongue color.
- A white tongue is an indicator of dehydration, fungal infections, common cold, influenza, and other infections. A thick white coating can also be a sign of intoxication. Candida albicans cause yeast infection (also known as the thrush), appearing as white cottage cheese-like colored plaques on the oral cavity’s mucosa, including the tongue. Leukoplakia also can be visible as white tongue coating.
- The pale color is an indicator of a weak immune system, malnutrition, and vitamin deficiency.
- Black color can cause tobacco and particular medication (antibiotics and medications containing chemical bismuth) usage, inappropriate oral hygiene, and radiation therapy. Very rarely black colored tongue has HIV and diabetes patients.
- Purple tongue presents in heart disorders and poor blood circulation, as well as in Kawasaki disease.
- The red tongue is a sign of scarlet fever, tongue inflammation or glossitis, vitamin B12 deficiency, and allergic reactions.
- Gray color can sign digestive tract diseases; sometimes, patients with eczema present with it.
- The blue color can be visible in heart and blood circulation disorders and kidney problems.
- The yellow color most commonly is seen in liver and stomach diseases, poor oral hygiene, smoking, and bacterial growth.
- Orange color is also an indicator of poor oral hygiene; patients with mouth dryness can have it, and particular food (carrots are high in beta carotene) and antibiotics present with it.
- The green color is a significator of poor oral hygiene, fungal infections.
Hairy tongue appears most commonly as furry black tongue coating because mainly of the filiform papillae overgrowth on the dorsal surface and keratin build up.
Hairy tongue happens because of lack of abrasion to the superior surface, leading to longer filiform papillae length. Food, tobacco, bacteria, and yeasts accumulate between them and give the typical appearance. Color can vary, but it is often black or brown; it can also be white, yellow, or green.
It is more common in smoking individuals and people with mouth dryness, poor oral hygiene, and drug addiction. People who often use antibiotics and certain medications are at higher risk, leading to changes in normal bacteria and yeast counts. Individuals who don’t have teeth, who drink excessive amounts of coffee, tea, and alcohol also have a higher risk of hairy tongue development. Most expected it affects older people and males.
Hairy tongue is not a life-threatening condition, and it is not harmful. It usually doesn’t have any symptoms, but sometimes a burning sensation can be present, or a tickling feeling, usually during swallowing as the long papillae touches the palate. A hairy tongue can lead to bad breath and taste changes (typically metallic) because of the accumulating bacteria and debris.
The best possible way to get rid of the hairy tongue is good oral hygiene with tongue brushing and scraping with toothbrushes or scrapers. If it doesn’t work, the hairy tongue can remove certain medications and surgical treatment.
The best possible prevention is good oral hygiene with regular tongue brushing as this condition tends to come back.
Summary on the tongue
What is the tongue?
The tongue is a pink mobile muscular digestive system’s organ covered by mucosa and located in the oral cavity proper part, extending to the oropharynx.
Is the tongue a muscular organ?
Yes, the tongue is a muscular organ.
What is the back of the tongue called?
The back of the tongue is the root part.
What are the main parts of the tongue?
The tongue has three main parts- the tip, the body, and the root.
What are the tiny bumps on the tongue called?
Tiny bumps on the tongue are lingual papillae.
Are there taste buds under the tongue?
No, there are no taste buds under the tongue. The superior or dorsal surface and the sides of the tongue contain taste buds.
Where are taste buds on your tongue?
Lingual papillae covering the superior or the dorsal surface of the tongue contains taste buds. They locate in the lingual papillae’s epithelium.
What papilla does tongue have?
The tongue has four types of papillae- filiform, fungiform, circumvallate, and foliate.
Where is the papilla of the tongue?
The papillae cover the dorsal surface.
How should the underside of a tongue look?
The ventral surface is relatively smooth. It is more pronounced at the tip and the anterior part of the tongue’s body areas.
What are two types of muscles of the tongue?
The tongue has four pairs of intrinsic and four pairs of extrinsic muscles.
What muscles move the tongue?
The tongue moves four pairs of extrinsic muscles. Genioglossus and hyoglossus muscles go below it, while styloglossus and palatoglossus above.
Is your tongue always moving?
The tongue contains skeletal muscles, which means you can control tongue movements, and you can move it if you want to.
Is your tongue the strongest muscle?
No, it is not the strongest muscle.
Are bumps of the back of the tongue normal?
Bumps on the back of the tongue are usual. In the pre-sulcal area close to the terminal sulcus, the nodes you can see are the circumvallate papilla. Still, after the terminal sulcus, lymphoid tissue looks bumpy.
What is the umami on your tongue?
Umami is the fifth taste, and the tongue provides it. Umami is the savory taste of glutamic acid and glutamate.
What are the five tastes?
Five tastes are sweet, salty, sour, bitter, and umami.
What are the main functions of the tongue?
The tongue has three main functions: mechanical food procession and food maneuvering in the oral cavity, taste, and speech formation.
What color is a healthy tongue?
A healthy tongue has a pink color. It can appear from a lighter to a darker shade.
What is a healthy tongue?
A healthy tongue has a pink color, it is mobile, and the dorsal surface has a rough texture with a thin white coating because of the many papillae.
How does a B12 deficiency look?
B12 deficiency can appear as a red tongue.
Why is the back of my tongue black?
Black color can cause tobacco and particular medication (antibiotics and medications containing chemical bismuth) usage, inappropriate oral hygiene, and radiation therapy. Very rarely black colored tongue has HIV and diabetes patients.
What sign is a white tongue?
A white tongue is an indicator of dehydration, fungal infections, common cold, influenza, and other infections. A thick white coating can also be a sign of intoxication.
What causes a hairy tongue?
Hairy tongue appears most commonly as furry black tongue coating because mainly of the filiform papillae overgrowth on the dorsal surface and keratin build up.
Can you get rid of the hairy tongue?
The best possible way to get rid of the hairy tongue is good oral hygiene with tongue brushing and scraping with toothbrushes or scrapers. If it doesn’t work, the hairy tongue can remove medication and surgical treatment.