Muscles of Facial Expression and Mastication

depressor labii inferioris

This muscle also originates on the mandible and inserts on to the orbicularis muscle. It depresses the bottom lip. (Names: depressor=depress, labii=lips, inferioris=below or bottom)

medial pterygoid

Also a muscle of mastication. Both pterygoid muscles are on the inside of the mandible. The medial pterygoid elevates the jaw and provides sideways jaw movement.

mentalis

The mentalis muscle originates on the chin and goes into the orbicularis oris muscle. It elevates and protrudes the lower lip. Basically, it allows for pouting.

risorius

The risorius originates on the side of the face and inserts on the orbicularis oris muscle. It draws the angle of the mouth laterally (to the side) and enables the human being to smile.

lateral pterygoid

This is a muscle of mastication. It originates from the pterygoid process of the sphenoid bone. It moves the mandible and limits sideways jaw movement.

depressor anguli oris

This muscle originates on the lower part of the mandible. It pulls down the angle of the mouth. (Names: depressor=depress, anguli=angle, oris=mouth)