The masseter muscle is a prominent facial muscle located in the jaw that plays a major role in mastication. The name comes from the Greek word masasthai, meaning “to chew”. It is only found in mammals and it is particularly powerful in herbivores to facilitate chewing of plant matter.

There are four pairs of muscles responsible for chewing movements or mastication:
• The temporalis
• The masseter
• The medial pterygoid
• The lateral pterygoid
All of these muscles connect to the mandible (lower jaw) and are some of the strongest muscles in the body. The four muscles work together to pull the jaw down and back up again. The masseter is the key muscle that pulls the mandible upward to close the mouth and bite down.

Structure
The masseter can be felt at the sides of the jaw when the teeth are clenched. It is a thick, rectangular-shaped, paired muscle that consists of two distinct sections – the ‘superficial’ and ‘deep’ portions.

Superficial portion
The larger, superficial portion of the masseter is the thick connective tissue (similar to a tendon) of the muscle that attaches to the zygomatic bone (cheekbone).

Deep portion
The smaller, deep portion contains more muscle tissue and it attaches to the mandible (lower jaw).

The Muscle That Exerts the Most Force
Based on surface area and weight, the masseter can exert more force than any other muscle in the body. The bite strength of an average man can be as much as 120 kilograms for the molar teeth. If your teeth could take the pressure, the masseter muscle would give you enough power to crack soft rocks or concrete.