In the context of facial muscle actions, what is the primary action of the zygomaticus major muscle?

• A. Depresses the lower lip and pulls the angle of the mouth downward (frowning)
• B. Elevates and draws the angle of the mouth laterally (smiling)
• C. Closes the eyelids by pulling the skin of the eyelid inferiorly
• D. Compresses the cheek against the teeth (as in blowing or chewing)

Answer: (B)

Verified step by step guidance

1. Step 1: Identify the muscle in question, which is the zygomaticus major. This muscle is located in the face and is involved in movements related to facial expressions.
2. Step 2: Recall the anatomical origin and insertion of the zygomaticus major. It originates from the zygomatic bone (cheekbone) and inserts into the skin and muscle at the angle of the mouth.
3. Step 3: Understand the direction of muscle fibers and their action. Since the muscle runs from the cheekbone to the corner of the mouth, contraction will pull the angle of the mouth upward and laterally.
4. Step 4: Connect this movement to facial expressions. Elevating and drawing the angle of the mouth laterally is associated with smiling.
5. Step 5: Compare this action with other options given, such as depressing the lower lip (frowning), closing eyelids, or compressing the cheek, which are actions of different muscles like the depressor labii inferioris, orbicularis oculi, and buccinator respectively.