Which of the following muscle is supplied by external laryngeal nerve which is a branch of superior laryngeal nerve
**Core Concept**
The **superior laryngeal nerve** is a branch of the **vagus nerve** that divides into the **internal laryngeal nerve** and the **external laryngeal nerve**. The external laryngeal nerve is primarily responsible for the motor supply to a specific laryngeal muscle.
**Why the Correct Answer is Right**
The **external laryngeal nerve** supplies the **cricothyroid muscle**, which is involved in tensing the vocal cords and thereby increasing the pitch of the voice. This muscle is unique among the laryngeal muscles as it is the only one not supplied by the **recurrent laryngeal nerve**.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it is not specified, but typically, other options might include muscles like the thyroarytenoid, which is supplied by the recurrent laryngeal nerve.
**Option B:** Incorrect for similar reasons as Option A, assuming it refers to a muscle not supplied by the external laryngeal nerve.
**Option C:** Incorrect as it is likely referring to a muscle not innervated by the external laryngeal nerve.
**Option D:** Incorrect as this option does not correspond with the known function of the external laryngeal nerve.
**Clinical Pearl / High-Yield Fact**
Remembering that the **cricothyroid muscle** is the only laryngeal muscle innervated by the **external laryngeal nerve**, a branch of the **superior laryngeal nerve**, is crucial for understanding laryngeal function and for clinical applications such as evaluating vocal cord paralysis.
**Correct Answer:** Correct Answer: D. Cricothyroid muscle