Washington Esthetician State Board Practice Exam 2025 – Complete Prep Resource

The orbicularis oris is the muscle responsible for facial expressions, particularly those involving movements of the mouth. This muscle encircles the mouth and plays a crucial role in actions such as puckering the lips, closing the mouth, and various expressions that involve the lips. It is essential for phonation, eating, and various nonverbal communication signals, contributing greatly to how we express emotions and react to stimuli.

Other muscles mentioned in the options have distinct functions unrelated to facial expressions. The deltoid muscle, for instance, is located in the shoulder and is responsible for arm movements. The rectus abdominis is a muscle in the abdomen that aids in trunk flexion and stabilization of the pelvis. The trapezius muscle, located in the upper back and neck, is primarily involved in moving and stabilizing the shoulder blades and head rather than facial features. Hence, the orbicularis oris is the correct answer as it is directly associated with facial expressions.