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The tongue is a unique muscle in the body which serves a number of different purposes, including eating and speaking. In terms of the anatomy of the tongue, it contains no bones, nor is covered by an outer layer of skin. It is most similar to the tentacles of an octopus or squid.
Among the most sensitive parts of the body, the tongue organ extends from the mouth through to the pharynx, and is about four inches (10cm) long. The anatomy of the tongue consists of a series of eight muscles, with a covering of mucous membrane and small bumps known as papillae. It is connected to the mouth by the frenulum, a thinly-layered stretch of tissue that prevents the tongue from being swallowed.
Sensation and taste on the tongue are provided by a great number of papillae, and the sensory receptors contained within them are known as taste buds. They are anchored by the glossopharyngeal nerve, the facial nerve, and the lingual nerve. These nerves, as well as the muscles of the tongue, are fed by the lingual artery and a network of smaller blood vessels.
The taste buds that cover the top of the tongue are composed of many tiny hairs known as microvilli. These are the taste cells that translate the chemicals of food into signals the brain interprets as bitter, sweet, sour, or salty. The number of taste buds declines over time, starting at roughly 10,000 and decreasing to around 5,000 after the age of 60.
While the taste buds may make eating enjoyable, it is the muscles of the tongue that make it mechanically possible. The teeth are responsible for segmenting food into sections suitable for swallowing, and the muscles at the back of the mouth move the pieces towards the esophagus. Once there, the act of swallowing sends them down the digestive tract.
In humans, the anatomy of the tongue is also crucial to the formation of words. The muscles at the back of the tongue are responsible for generating many hard consonant sounds, while the front of the tongue handles fricatives. These various parts of the tongue work in conjunction with each other and with the teeth to create advanced sounds, such as dipthongs.
Tonsils are another part of the anatomy of the tongue. Around the tongue are the lingual tonsil and the palatine tonsils. These small collections of tissue near the back and sides of the mouth do not participate in the creation of sounds or the process of eating, but are part of the immune system. Tonsils act as a filter, sifting out bacteria and other germs that can infect the body.