Which facial muscle action is primarily responsible for frowning by pulling the eyebrows inferiorly and medially?

• A. Contraction of the zygomaticus major
• B. Contraction of the frontalis (frontal belly of occipitofrontalis)
• C. Contraction of the corrugator supercilii
• D. Contraction of the orbicularis oculi

Answer: (C)

Verified step by step guidance

1. Identify the facial muscles involved in eyebrow movement and their primary actions.
2. Understand that the zygomaticus major is mainly responsible for elevating the corners of the mouth, contributing to smiling, not frowning.
3. Recognize that the frontalis (frontal belly of occipitofrontalis) elevates the eyebrows, causing expressions like surprise, which is opposite to frowning.
4. Know that the orbicularis oculi primarily functions to close the eyelids and is not involved in pulling the eyebrows downward or medially.
5. Conclude that the corrugator supercilii muscle contracts to pull the eyebrows inferiorly and medially, creating the characteristic frown by drawing the eyebrows together and downward.