INTRODUCTION
The tongue is a muscular organ in the mouth. The tongue is covered with moist, pink tissue called mucosa. Tiny bumps called papillae give the tongue its rough texture. Thousands of taste buds cover the surfaces of the papillae. Taste buds are collections of nerve-like cells that connect to nerves running into the brain.
The tongue is anchored to the mouth by webs of tough tissue and mucosa. The tether holding down the front of the tongue is called the frenum. In the back of the mouth, the tongue is anchored into the hyoid bone. The tongue is vital for chewing and swallowing food, as well as for speech.
The four common tastes are sweet, sour, bitter, and salty. A fifth taste, called umami, results from tasting glutamate (present in MSG). The tongue has many nerves that help detect and transmit taste signals to the brain. Because of this, all parts of the tongue can detect these four common tastes; the commonly described “taste map” of the tongue doesn’t really exist.
Tongues are measured from the epiglottis to the tip. An adult man's average tongue length is 3.3 inches (8.5 cm), and an adult woman's average tongue length is 3.1 inches (7.9 cm).
The average adult has between 2,000 to 4,000 taste buds in total. The sensory cells in the taste buds responsible for how we perceive taste renew themselves.
About one-quarter of the population is considered "supertasters," people with a heightened sense of taste, particularly for bitter foods. Another quarter is considered "nontasters," who fortunately can taste foods.
Taste buds not visible to the human eye. Those little pink and white bumps you do see on your tongue are actually called papillae, hair-like projections that taste buds rest atop. Each has an average of six taste buds buried inside its surface tissue.
Most of your taste buds cannot be seen with the naked eye. What you are seeing that appear to be the taste buds are taste papillae, which are small buds that contain sensory nerve cells responsible for the sense of taste.
There are three types of papillae: fungiform, circumvallate, and foliate. Fungiform papillae are most common and are found mostly at the tip of the tongue and at the edges. These papillae cannot be seen with the naked eye.
The other two types of papillae are less common but can be seen with the naked eye. Circumvallate papillae are large and found arranged in a V-shape at the back of the tongue, near the throat. There are only 7 to 12 circumvallate papillae, which are round and raised. We also have about 20 foliate papillae on the back edges of the tongue, which are also visible to the naked eye.
It's true most taste buds are on your tongue, but there are also taste cells in the back of your throat, on your epiglottis (that flap of cartilage in the mouth at the back of the tongue), your nose and sinuses, all the way down the throat to the upper part of the esophagus. Infants and young children have even more cells that sense taste in the mucous membranes of their lips and cheeks. All these cells send signals to the brain that are converted into what we perceive as taste.
We grew up believing the tongue had four taste zones: one each for sweet, sour, salty, and bitter, but this is not the case. These tastes, along with a fifth taste called umami (savory), can be sensed on all parts of the tongue. The sides of the tongue are more sensitive overall than the middle, and the back of our tongue is more sensitive to bitter tastes.
The tongue is all muscle, but not just one muscle – it's made up of 8 different muscles that intertwine with each other creating a flexible matrix, much like an elephant's trunk. It's called a muscular hydro stat, and the tongue muscles are the only muscles in the human body that work independently of the skeleton. Your tongue muscles do have amazing stamina and are used constantly for eating, talking, and swallowing. The tongue just never seems to get tired!
Taste buds have helped us evolve as humans. In the beginning, the sense of taste helped us test the foods we ate: bitter and sour tastes might indicate poisonous plants or rotting foods. The back of our tongue is sensitive to bitter tastes so we can spit out poisonous or spoiled foods before we swallow them. Sweet and salty tastes let us know foods were rich in nutrients.
If you get fat, so does your tongue! The human tongue has a high percentage of fat, and there is a correlation between tongue fat volume and obesity. A study in the journal Sleep showed that having a larger tongue with higher levels of fat might be a risk factor for obstructive sleep apnea, in which a person repeatedly stops and starts breathing while sleeping) in obese adults.
Every person's tongue is unique, and similar to fingerprints some see the potential for the tongue to act as an identify verification tool. The tongue is protected in the mouth and would be difficult to forge, and a person can stick it out for examination. Researchers are working on ways to use the tongue as a biometric authenticator – a reliable way to positively identify a person.
Your tongue can actually provide clues about your overall health.
- A bright red tongue may be a sign of folic acid or B12 deficiency, scarlet fever, or Kawasaki disease (a serious condition seen in children)
- White spots or a white coating on the tongue could indicate oral thrush (a type of yeast infection), or leukoplakia (which can be a precursor to cancer)
- A black, hairy tongue can be a sign of bacterial overgrowth, and can also occur in people with diabetes or those on antibiotics or chemotherapy
- Painful bumps on the tongue may be canker sores (mouth ulcers), or oral cancer.
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