The fourth pharyngeal arch is associated with which cranial nerve and branches?

The fourth pharyngeal arch is associated with which cranial nerve and branches?

• A. CN X; superior laryngeal branches
• B. CN X; recurrent laryngeal branches
• C. CN IX; superior laryngeal branches
• D. CN XI; superior laryngeal branches

Answer: (A)

The fourth pharyngeal arch is innervated by the vagus nerve (cranial nerve X). Its contributions to the larynx travel with the superior laryngeal branch of CN X. This branch splits into an internal branch, which provides sensation above the vocal cords, and an external branch, which motorizes the cricothyroid muscle. The recurrent laryngeal nerve, which innervates most intrinsic laryngeal muscles, comes from the sixth arch, not the fourth. So the fourth arch is best matched with CN X and its superior laryngeal branches.

The fourth pharyngeal arch is innervated by the vagus nerve (cranial nerve X). Its contributions to the larynx travel with the superior laryngeal branch of CN X. This branch splits into an internal branch, which provides sensation above the vocal cords, and an external branch, which motorizes the cricothyroid muscle. The recurrent laryngeal nerve, which innervates most intrinsic laryngeal muscles, comes from the sixth arch, not the fourth. So the fourth arch is best matched with CN X and its superior laryngeal branches.