Which muscle of larynx is not supplied by recurrent laryngeal nerve?
**Core Concept**
The laryngeal muscles are innervated by the recurrent laryngeal nerve (RLN) and the external branch of the superior laryngeal nerve (EBSLN). The RLN supplies all the intrinsic muscles of the larynx except one, which is primarily responsible for vocal cord tension.
**Why the Correct Answer is Right**
The cricothyroid muscle is responsible for elongating and tensing the vocal cords. It is the only intrinsic laryngeal muscle that is not supplied by the recurrent laryngeal nerve. Instead, it is innervated by the external branch of the superior laryngeal nerve (EBSLN). This is because the EBSLN is responsible for regulating vocal cord tension and pitch.
**Why Each Wrong Option is Incorrect**
* **Option A:** The posterior cricoarytenoid muscle is the only abductor of the vocal cords and is supplied by the recurrent laryngeal nerve.
* **Option B:** The lateral cricoarytenoid muscle is an adductor of the vocal cords and is supplied by the recurrent laryngeal nerve.
* **Option D:** The thyroarytenoid muscle is also an adductor of the vocal cords and is supplied by the recurrent laryngeal nerve.
**Clinical Pearl / High-Yield Fact**
The cricothyroid muscle is the only intrinsic laryngeal muscle that can be used to assess the integrity of the external branch of the superior laryngeal nerve (EBSLN). This is an important clinical correlation for ENT surgeons and anesthesiologists.
**Correct Answer: C. Cricothyroid muscle.**