All of the following laryngeal muscles are adductors of vocal cord except:
**Core Concept**
The laryngeal muscles play a crucial role in regulating voice production by controlling the movement of the vocal cords. The **intrinsic laryngeal muscles** are responsible for this function, with some muscles acting as adductors and others as abductors of the vocal cords.
**Why the Correct Answer is Right**
The correct answer is the muscle that is not an adductor of the vocal cord. In the larynx, the muscles responsible for adduction (bringing together) of the vocal cords include the **lateral cricoarytenoid**, **thyroarytenoid**, and **interarytenoid** muscles, among others. The **posterior cricoarytenoid** muscle, however, is the only intrinsic laryngeal muscle that acts as an abductor of the vocal cord, opening the glottis by rotating the arytenoid cartilages outward.
**Why Each Wrong Option is Incorrect**
**Option A:** This would be incorrect if it listed an adductor muscle.
**Option B:** Similarly, if this option named an adductor, it would be wrong.
**Option C:** If this choice also referred to an adductor muscle, it would not be the correct answer.
**Option D:** Assuming this option is the **posterior cricoarytenoid**, it would be correct because it's the abductor, not an adductor.
**Clinical Pearl / High-Yield Fact**
Remembering that the **posterior cricoarytenoid** muscle is the sole abductor of the vocal cords is crucial for understanding laryngeal function and for diagnosing conditions related to vocal cord paralysis.
**Correct Answer:** D. posterior cricoarytenoid muscle