Chewing (also called mastication ) is a mechanical process that is used to chop up food and its first enzymatic breakdown ( digestion ). This results in an "up-down movement" in combination with a sideways or forward-backward movement of the lower jaw . The masticatory system is also called the craniomandibular system . As a result, the food in the mouth is transported between the molar teeth with the tongue and is ground by them. When chewing, the food is mixed with the saliva .
Most vertebrates cannot chew, neither fish nor amphibians or birds . Snakes, for example, devour their prey without chewing it. Other animals tear pieces out of the prey, such as birds of prey or crocodiles . Many mammals cannot chew either, such as the Echidna . Most predators such as dogs and cats chew their food very little and choke down larger pieces.
Chewing, on the other hand, is particularly pronounced among the cattle , who, as ruminants, chew their food twice by conveying the pre-digested food pulp from the stomach through the esophagus and into the mouth. The necessity of chewing depends to a large extent on the food, the more it contains cellulose , for example grass , bark, etc., the more important the mechanical comminution of the food becomes.
Herbivores , who have not developed the evolutionary advantage of chewing in the mouth using molars, are dependent on more aggressive digestive juices and on swallowed stones, which take over the mechanical grinding of the plant fibers ( gizzards ).
The pathological chewing on the fingernails in humans is called onychophagia .