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Mucus cells.

Mucus (mucous), or slime, is a slippery liquid. It is made by many living things as a kind of biological lubricant. It plays the role in living things which oil plays in machines.

Mucus is mainly composed of polysaccharides, which are long-chain carbohydrates. These molecules are stiff when dry, and sticky and slippery when wet. They are present in all types of organisms from bacteria to humans.