Mastication or chewing is the process by which food is torn and/or crushed by teeth. It is the first step of digestion. Through chewing, the food is made softer and warmer and the enzymes in saliva begin to break down carbohydrates in the food.

After chewing, the food (now called a bolus) is swallowed. It enters the esophagus and continues on to the stomach, where the next step of digestion occurs.

Mastication is chiefly possible thanks to powerful muscles, masseter and temporalis, as well as smaller muscles that allow fine control. They move the mandible against the upper jaw and enable crushing of relatively hard food.

In humans, the mandible is connected with the temporomandibular joint that permits forward-backward and side to side movement.

Some animals, called ruminants, chew food more than once. These animals, such as cows, chew their food more than once for the extra nutrients in it. This food is called "cud".

Muscles of mastication

Chewing food is a complex technique, muscles need to be powerful enough to break tough portions of food, yet have enough dexterity to not injure the tongue, and to clear the mouth completely.

All the muscles of mastication (except stylopharyngeus ) are supplied by the mandibular nerve (V₃), which is a branch of the trigeminal nerve that mostly carries sensation from the face.

Temporalis is a muscle attached to the temporal fossa (on the side of the skull) and connects to the coronoid process of the mandible. It acts to close the jaw, and also pull the mandible inwards (retrude it). The masseter starts at the zygomatic arch and inserts at the lateral surface of the mandible.

All muscles of human mastication

Important muscles in bold.

• Buccinator muscle
• Depressor anguli oris muscle
• Depressor labii inferioris muscle
• Lateral pterygoid muscle
• Levator anguli oris muscle
• Levator labii superioris alaeque nasi muscle
• Levator labii superioris muscle
• Levator veli palatini muscle
• Masseter muscle
• Medial pterygoid muscle
• Mentalis muscle
• Orbicularis oris muscle
• Superior pharyngeal constrictor muscle
• Temporalis muscle
• Tensor veli palatini muscle
• Zygomaticus major muscle
• Zygomaticus minor muscle