Whether you’re a novice or a pro in the world of facial expressions, there are always pesky details that can trip you up. Every muscle has its own quirks, properties, and inevitable variations. Some muscles, like the frontalis (basic brow elevator), are straightforward. Others are just not that simple. 

Orbicularis oris is one of those tricky muscles. Its complex structure and muscle fiber arrangements give it the ability to form a number of intricate shapes and positions. Think about all of the nuanced mouth movements that go into speech; orbicularis oris is responsible for many of them!

Here we will cover two particular orbicularis oris expressions that often get confused: lip tightener, horizontal type (See FACS Cheat Sheet for clarification on vertical vs. horizontal types.) AKA AU23 and lip presser AKA AU24 .

Let’s start by watching the attached video demo.