Depressor labii inferioris:
A. Is also called the “laughing muscle”
B. Pulls the angle of the mouth upward and laterally
C. Draws the lower lip down and laterally
D. Assists in expressions of doubt
E. A&B
F. C&D
The Correct Answer and Explanation is :
The correct answer is C. Draws the lower lip down and laterally.
Explanation:
The depressor labii inferioris is a facial muscle responsible for depressing and everting the lower lip. It originates from the lateral surface of the mandible, below the mental foramen, and inserts into the skin of the lower lip, blending with the orbicularis oris muscle. This muscle is innervated by the marginal mandibular branch of the facial nerve. citeturn0search1
Functions:
- Depression of the Lower Lip: The primary function of the depressor labii inferioris is to draw the lower lip downward, as seen when expressing sadness or doubt.
- Eversion of the Lower Lip: It also everts the lower lip, which is important for actions like pouting.
Clarification of Other Options:
- A. Is also called the “laughing muscle”: This is incorrect. The “laughing muscle” refers to the zygomaticus major, which elevates the corners of the mouth during smiling.
- B. Pulls the angle of the mouth upward and laterally: This describes the action of the zygomaticus major, not the depressor labii inferioris.
- D. Assists in expressions of doubt: While the depressor labii inferioris contributes to facial expressions, it is more directly associated with sadness or frowning rather than doubt.
- E. A & B: Since both A and B are incorrect, this option is also incorrect.
- F. C & D: While C is correct, D is not, making this option incorrect.
In summary, the depressor labii inferioris muscle is primarily responsible for depressing and everting the lower lip, contributing to facial expressions such as sadness or pouting.