International Board of Certified Lactation Consultant (IBCLC) Practice Exam

Which muscle is primarily responsible for forming the lips?

1. Orbicularis Oris

2. Masseter

3. Buccinator

4. Zygomaticus

The correct answer is: Orbicularis Oris

The orbicularis oris muscle is primarily responsible for forming the lips due to its unique circular arrangement around the mouth. Its primary function is to control the movements of the lips, including actions such as closing the mouth, puckering, and kissing. This muscle is crucial for various functions such as speaking, eating, and facial expression. In contrast, the masseter muscle is primarily involved in the process of chewing by elevating the mandible, but it does not directly contribute to the structure of the lips. The buccinator muscle, located in the cheek, assists with eating and helps in blowing air but is not primarily responsible for lip formation. The zygomaticus muscle is involved in facial expression, specifically elevating the corners of the mouth to smile, but it does not shape or define the lips themselves. Therefore, the orbicularis oris is the key muscle involved in the formation and function of the lips.