Recurrent laryngeal nerve supplies all EXCEPT:
**Core Concept**
The recurrent laryngeal nerve is a branch of the vagus nerve that supplies the intrinsic muscles of the larynx, except for the cricothyroid muscle. It plays a crucial role in voice production and swallowing. The nerve's anatomical course and distribution are essential for understanding its function.
**Why the Correct Answer is Right**
The correct answer is related to the specific muscles of the larynx that are not supplied by the recurrent laryngeal nerve. The cricothyroid muscle, which is responsible for tensing the vocal cords, is actually innervated by the external branch of the superior laryngeal nerve, another branch of the vagus nerve.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the recurrent laryngeal nerve does supply the posterior cricoarytenoid muscle, which is the only muscle to open the glottis.
**Option B:** This option is incorrect because the recurrent laryngeal nerve supplies the lateral cricoarytenoid muscle, which helps to adduct and tense the vocal cords.
**Option C:** This option is incorrect because the recurrent laryngeal nerve supplies the thyroarytenoid muscle, which helps to relax and shorten the vocal cords.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the recurrent laryngeal nerve supplies all the intrinsic muscles of the larynx except for the cricothyroid muscle, which is innervated by the external branch of the superior laryngeal nerve. This knowledge is critical for understanding vocal cord function and managing conditions like vocal cord paralysis.
**Correct Answer:** D. Cricothyroid muscle.