Anatomy of the Tongue

Taste is said to be the sense that people would most likely give up if they had to choose one, according to Bill Bryson in his book “The Body”. It also happens to be the least studied of the five senses. Despite this, the tongue performs some amazing jobs for you! It helps you soften and taste food, and swallow it, suck liquids (no more drinking through a straw!) and it also allows you to form the sounds you need for speech.

The tongue is an entirely muscular organ made up of eight muscles in total, and is unique as it is the only muscle in the body that isn't connected to a bone at both of its ends. Four of these muscles are classified as intrinsic: they are not attached to any bone and are able to change the shape of the tongue. The other four are extrinsic, where they are anchored to bone and change the position of the tongue.

Muscles

The intrinsic muscles are the superior longitudinal muscle, inferior longitudinal muscle, transverse muscle and vertical muscle. The extrinsic muscles are the genioglossus muscle (attached to the mandible), hyoglossus muscle (attached to the hyroid bone), styloglossus muscle (attached to the styloid process of the temporal bone) and palatoglossus muscle (attached to the palatine aponeurosis).

The genioglossus allows the tongue to extend outside of the mouth, the hyoglossus brings it back inside and allows it to be depressed, the styloglossus draws the sides of the tongue up to create a trough for swallowing and the patoglossus elevates the back of the tongue for swallowing.

Surface

The upper surface of the tongue is covered by rough bumps (or projections) of its mucous membrane, known as papillae. These papillae increase the tongues surface area and also provide protection for the taste buds.

Taste buds are sensory receptors that are renewed on a weekly basis that allow a person to taste whatever is in their mouth, however it is known that each person tastes things differently to the next. This is because the number of taste buds varies from person to person - it is estimated that adults can have anywhere between 2,000 – 10,000 taste buds in total, and that includes taste buds found in the throat and sides of the mouth. Some papillae also don’t help with the tasting process, they are there to provide abrasion to help break down the food when chewing.

Taste Sensations

Firstly, you may have been taught that taste is carried out on certain areas of the tongue, but this is a myth – the receptors that pick up the different tastes are distributed all over the tongue.

The taste buds also only work if the food eaten is firstly broken down by saliva. Once this happens, they can detect five tastes:

Salty - caused by salts, including bicarbonate of soda
Sweet - caused by carbohydrates, including fructose, sucrose and artificial sweeteners
Sour - caused by acidic compounds, including vinegar
Savoury (called umami) - “the food that tastes meaty”, such as cheese, mushrooms and chicken
Bitter – often caused by food with alkaline pH, including raw vegetables, cocoa and black coffee.

Tongue related AnatomyStuff resources:

Tongue Anatomy Model (2.5 times life size)

3B MICROanatomy Tongue Model

Ear, Nose and Throat Chart / Poster - Laminated

Further reading / sources

Muscles of the tongue 
https://www.kenhub.com/en/library/anatomy/muscles-and-taste-sensation-of-the-tongue 
Taste buds 
https://www.ncbi.nlm.nih.gov/books/NBK279408/ 
Tongue Map 
http://cst.ufl.edu/that-neat-and-tidy-map-of-tastes-on-the-tongue-you-learned-in-school-is-all-wrong.html 
Smell is the least studied sense 
https://news.virginia.edu/content/sense-taste-psychology-professor-examines-taste-system

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