The heart may be the hardest working muscle in the human body, but the tongue, which is made up of groups of muscles, is pretty tough as well.

Like the heart, the tongue is always working. When a person eats, it helps in the mixing process of foods. When a person speaks, it binds and contorts itself to form letters. It also contains linguinal tonsils to filter out germs. Even when a person is sleeping, the tongue is constantly pushing saliva down the throat.

It's also a unique feature of the human body. Similar to fingerprints, everyone also has a unique tongue print. Seeing the tongue's potential as a identify verification tool, Chinese researchers have recently been working on a 3D tongue image database.

According to the Guinness Book of World Records, Stephen Taylor of Coventry, England (not KISS front man Gene Simmons) has the longest tongue in the world at 9.8 cm. (3.86 in) measured from the tip to the middle of his closed top lip.

Illustration by Raffi Anderian

Compiled by Toronto Star Library

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