**Question:** Recurrent laryngeal nerve supplies all EXCEPT which of the following structures?

A. Cricothyroid muscle
B. Laryngeal branch of the vagus nerve
C. Vocal cords
D. Stem cells

**Core Concept:**
Recurrent laryngeal nerve (RLN) is a branch of the vagus nerve (CN X) that plays a crucial role in the innervation of the larynx. It consists of two divisions: the superior laryngeal nerve (SLN) and the inferior laryngeal nerve (ILN). The SLN supplies the cricothyroid muscle, while the ILN innervates the vocal cords (cricothyroid muscle and the intrinsic laryngeal muscles). The RLN does not supply the vocal cords directly; instead, it provides motor innervation to the cricothyroid muscle, which in turn influences the movement of the vocal cords.

**Why the Correct Answer is Right:**
The recurrent laryngeal nerve supplies all structures except the one that it doesn't innervate directly. In this case, the correct answer is D (stem cells) because stem cells are not a specific laryngeal structure or function that the RLN is responsible for. The RLN primarily influences the cricothyroid muscle, which is responsible for vocal cord movement.

**Why Each Wrong Option is Incorrect:**
A) The cricothyroid muscle is supplied by the superior laryngeal nerve (part of the recurrent laryngeal nerve), making this option incorrect.
B) The laryngeal branch of the vagus nerve (including RLN) supplies the vocal cords indirectly through the cricothyroid muscle, making this option incorrect.
C) The vocal cords are innervated directly by the recurrent laryngeal nerve (RLN), making this option incorrect.

**Clinical Pearl:**
The recurrent laryngeal nerve plays a vital role in maintaining the normal function of the larynx and voice production. A better understanding of its anatomy and function can help with interpreting various clinical scenarios, such as hoarseness, stridor, or vocal cord paralysis caused by RLN injury or disease.