Tongue: Anatomy, Function, and Common Disorders

The tongue is a mobile, muscular organ that lies within the mouth and partly extends into the upper throat. The tongue's anatomy is complex; it involves interlacing muscles, nerves, and a blood supply.

This article will explain the details of tongue anatomy and how each part contributes to its movements and to functions such as eating, taste, swallowing, speech, and even breathing. It will describe what a "normal" tongue should look like, ideas on how to keep your tongue healthy, and what signs might indicate a problem with your tongue.

Tongue Function

The tongue is a mass of muscles covered by a mucous membrane that is important for taste sensation. Beyond its obvious role in eating—manipulating food into a bolus that can be safely passed into the throat with swallowing—it also has a vital contribution to speech. It may even affect breathing, especially in sleep.

Eating

Consider how the tongue helps a person to eat food and swallow liquids. After the teeth have taken a bite with the help of the powerful muscles of the jaw, this food must be broken down into smaller pieces before it can be safely swallowed.

The tongue actively moves the food within the mouth, positioning it for further degradation by the teeth. The food is mixed with saliva, ultimately becoming a manageable portion called a bolus that may be moved into the pharynx before being swallowed and passing via the esophagus into the stomach. The tongue may also help with oral cleansing, keeping food from prolonged contact with the teeth.

The tongue helps to identify what might be safe and palatable to eat, with the sense of taste as detected by the taste buds. The basic taste sensations include:

• Sweet
• Salty
• Sour
• Bitter
• Savory (umami)

Although different regions of the tongue may be more sensitive to specific tastes, it is not as regionally distinct as was previously believed.

Speech

The tongue is also the main contributor to speech. It is not possible to form words and speak without the proper positioning of the tongue. This is dependent on muscles that alter the shape and position of the tongue.

The tongue anatomy makes it possible for you to articulate sounds appropriately. Dysfunction of the tongue may lead to a serious speech impediment.

Breathing

If the tongue sits too far back within the throat, it may affect breathing. This is more likely to occur when mouth breathing is present. With normal nasal breathing, the mouth is kept closed, and the lower jaw will be held in a more forward position as the teeth come together.

This reduces the potential for the tongue to obstruct the airway. In sleep, the shift of the tongue that happens with mouth breathing may cause problems including snoring and obstructive sleep apnea. Weight gain may increase the size of the tongue and make this worse.

Other Roles

The tongue has several other important roles. It may protect the body with a gag reflex, preventing unpalatable and even poisonous substances from being consumed. If the posterior part of the tongue is touched, there may be a strong muscular contraction of the throat, closing it off.

In addition, the tongue allows a path of rapid absorption of medications. Sublingual nitroglycerin, for example, is used to dilate the heart’s blood vessels when severe chest pain is occurring. With a pill or spray applied under the tongue, the medication quickly dissolves and enters the veins.

Tongue Anatomy

The tongue is a mass of muscle that can be divided into different parts based on its landmarks. This differentiation is helpful to connect its structure to specific unique functions.

Location

The tongue is found in the mouth and the upper throat. Key elements include:

• Muscles: The interwoven tongue muscles are categorized as either intrinsic muscles (entirely within the tongue, like the longitudinal muscles that help to curl the tip) and extrinsic muscles (those that originate outside the tongue). Extrinsic muscles that attach to the tongue and surrounding bone include the palatoglossus, which elevates the tongue and is more a part of the soft palate in your mouth.
  
• Nerves: All tongue muscles rely on various nerves for sensation, including the glossopharyngeal nerve and the internal laryngeal nerve, a branch of the vagus nerve. These sensations include touch and temperature (about two-thirds served by the lingual nerve). Taste is a special sensation and it comes from the chorda tympani nerve, branching from a facial nerve.
• Blood supply: The arteries of the tongue derive from the lingual artery, which arises from the external carotid artery. The venous drainage includes the dorsal lingual vein and deep lingual veins, emptying into the internal jugular vein. The veins under the tongue may be enlarged and tortuous (varicose) in older people, which may be associated with other health conditions.

Taste Buds

The bumps on the tongue are called papillae (from a Latin root meaning “nipple”) and these vary in shape and location and are associated with taste buds (though some have other purposes). The papillae may have different shapes, sizes, and functions.

The back of the tongue has no papillae, but underlying lymphatic tissue may give it an irregular, cobblestone appearance. Consider these general findings about papillae:

• Vallate papillae: These large, flat-topped bumps lie just in front of the terminal sulcus, located about two-thirds back on the surface of the tongue. They are surrounded by deep trenches—into which ducts open from fluid-producing glands—and their walls are covered in taste buds.
• Folate papillae: Though poorly developed in humans, these small folds of the mucosa surface of the tongue are found to the sides. They also have taste receptors located in taste buds.
• Filiform papillae: Lying in V-shape rows parallel to the terminal sulcus, these bumps are elongated and numerous. They contain nerve endings that are sensitive to touch.
• Fungiform papillae: Scattered among the filiform papillae are these mushroom-shaped spots that may be pink or red in coloration. They are most commonly found along the tip or sides of the tongue. Many contain receptors for taste within taste buds.

Parts of the Tongue

When looking at the tongue's surface, it is possible to divide the tongue into five general parts. This is important because different parts of the tongue may be supported by distinct nerves and blood vessels.

The lingual frenulum is a large midline fold of mucosa that passes from the tongue side of the gums (or gingiva) to the lower surface of the tongue. The frenulum connects the tongue to the floor of the mouth while allowing the tip to move freely. It is notable that the submandibular salivary gland (under your jaw) has a duct that opens beneath the tongue, passing saliva into the mouth here.

The visible parts of the tongue include:

• Root: This is most often defined as the back third of the tongue. It sits low in the mouth and near the throat, and it is relatively fixed in place. It is attached to the hyoid bone and mandible (lower jaw). It is close in proximity to two muscles: the geniohyoid and mylohyoid muscles.
• Body: The rest of the tongue, notably the forward two-thirds that lie in front of the sulcus. It is extremely mobile and serves multiple functions.
• Apex: This is the tip of the tongue, a pointed portion towards the front of the mouth. It is also extremely mobile.
• Dorsum: This is the curved upper surface towards the back. It has a V-shaped groove on it called the terminal sulcus.
• Inferior surface: Underneath the tongue lies this last feature, important for the ability to visualize veins that allow for the rapid absorption of specific medications.
  

Tongue Disorders

There are a handful of conditions affecting the tongue, often impacting the ability to swallow or speak normally. Some are present from birth, and others may develop from an infection or exposure to cancer-causing substances. Symptoms of disorders affecting the tongue can include:

• Speech difficulties, like dysphonia or dysarthria related to multiple sclerosis (MS)
• Changes in taste (this can happen with Bell's palsy or with chemotherapy, too)
• Sores or bumps on the tongue that can be infection or inflammation
• Discoloration, as with white or pink patches of benign migratory glossitis
• Numbness (for various reasons including MS, medication, or nerve damage)
• Burning sensation (burning mouth syndrome)

Other conditions that affect the tongue include the following.

Ankyloglossia

As noted above, the lingual frenulum (from the Latin word meaning “bridle”) is a small fold of mucous membrane that connects the middle of the lower surface of the tongue to the floor of the mouth. If it is too short, often from birth, the tongue may be abnormally retracted into the lower jaw.

This lower position leads to a condition that is colloquially known as being “tongue tied.” This may be rarely checked (or simply ignored), especially if it is at the back of the tongue, and often goes untreated. It may be recognized with early infancy swallowing problems and speech impairment at school age as the short frenulum may interfere with tongue movements and function.

Clipping the frenulum is a simple surgery and this frenulectomy may be necessary for infants to free the tongue for normal speech development.

Genioglossus muscle paralysis

When this muscle becomes paralyzed, the tongue falls backward, potentially obstructing the airway and increasing the risk of suffocation. Total relaxation of the tongue occurs during general anesthesia. As such, this shift of the tongue must be prevented to avoid blocking the airway. This is usually accomplished by inserting a temporary breathing tube during surgery.

This airway obstruction also can occur with obstructive sleep apnea.

Hypoglossal nerve injury

Trauma to the lower jaw (mandible) may cause a fracture that injures the hypoglossal nerve, resulting in paralysis and eventual shrinking of one side of the tongue. After the injury, the tongue deviates to the paralyzed side when protruded.

Lingual carcinoma

Cancer, or carcinoma, may affect the tongue. This is more likely due to infections from human papillomavirus (HPV) or from the use of tobacco, including chewing or smoking.

The back of the tongue has lymphatic drainage that may cause aggressive cancers to metastasize to the superior deep cervical lymph nodes on both sides of the neck. Tongue cancer may require surgical treatment, radiation therapy, and even chemotherapy if metastatic.

Thyroglossal duct cyst

Rarely, there can be a cystic remnant of the thyroglossal duct found within the root of the tongue. Most of these cysts lie close to the body of the hyoid bone, producing a painless swelling of the neck at the midline. It may connect with a fistula to the skin’s surface, leading to a non-healing sore (called a thyroglossal fistula) at the neck. Surgery may be required for the resolution of the problem.

Aberrant thyroid gland

The thyroid gland typically descends within the embryo along the thyroglossal duct. In some cases, remnants of the thyroid gland may remain behind. These may be found in the root of the tongue or even in the neck.

In some cases, it may be treated with radioactive iodine and long-term thyroid replacement for post-surgical hypothyroidism is necessary.

Other conditions

There are a few other conditions that may be associated with the tongue, such as:

• Candidiasis: A yeast infection commonly known as thrush is caused by Candida albicans that may cause a white-colored plaque on the mucosa lining the tongue and mouth. It occurs more among the immune-suppressed, especially among the young and old.
• Hairy tongue syndrome: The tongue may appear white or black due to overgrowth of the papillae on the surface of the tongue. A thorough scraping may clear off the debris and resolve the unpleasant appearance and associated smell.
• Macroglossia: Literally a big tongue, this condition may affect the ability to swallow or breathe normally. It may occur in the setting of Down syndrome, weight gain, or hypothyroidism.
• Sleep apnea: The tongue size and position may increase the risk for sleep apnea due to obstruction of airflow within the throat.

How to Keep Your Tongue Healthy

For most people, basic hygiene steps can help to keep your tongue healthy. So can a few lifestyle changes. These steps include:

• Brushing your tongue each day, just as you do your teeth. You also should brush the inside of your mouth and cheeks.
• Checking your tongue for sores, spots, and other concerns.
• Ensuring that you keep routine dental visits. These visits include a check for oral cancers that can affect the tongue.
• Stopping smoking, which can increase the risk of tongue cancer and other oral cancers
• Considering any food sensitivities that may affect the tissues of your tongue

Consider the HPV vaccine, if eligible. HPV infection is linked to tongue and oral cancer risk. And for some people diagnosed with dysphagia (difficulty swallowing) or another tongue-related condition, exercises to strengthen your tongue may help.

Depending on tests results (imaging, biopsy) and your diagnosis, other interventions including surgery may be needed.

Summary

The tongue is critical to your overall health, though you likely don't often think about tongue anatomy and function. A healthy tongue and its combination of muscles, nerves, and blood vessels make it possible for you to speak, eat and swallow, breathe properly, or absorb medications like sublingual nitroglycerin.

Quite a few conditions, however, can affect the tongue. They range from relatively common and highly treatable yeast infections, like thrush, to potentially life-threatening cancers.

Steps you can take to improve your tongue health include routine brushing and dental visits. Talk to your healthcare provider if you have specific concerns: they can diagnosis a condition affecting your tongue and discuss treatment options with you.