On either side of the mouth there is a pair of strong, short and triangular mandibles or jaws. Each mandible has several dark grooves on the inside. These grooves are called molar processes or denticles. Each mandible has two types of muscles. These are-
(i) Adductor muscle: The muscle on the inner side of the mandible is called adductor muscle. It contracts and pulls the mandible inwards.
(ii) Abductor muscle: The muscle on the outer side of the mandible is called the abductor muscle. It contracts and pulls the mandible outward. The work of the mandible is to bite and crush the food.
