An infant develops a weak, hoarse cry immediately after surgical ligation of a patent ductus arteriosus. The injured nerve supplies muscles derived from which pharyngeal arch?

• A Second pharyngeal arch
• B Third pharyngeal arch
• C Fourth pharyngeal arch
• D Sixth pharyngeal arch ✓

Explanation

The left recurrent laryngeal nerve loops under the ductus arteriosus (ligamentum arteriosum after birth) and can be injured during its ligation. It supplies all intrinsic laryngeal muscles except the cricothyroid, and these muscles are derived from the sixth pharyngeal arch. Cricothyroid, supplied by the external laryngeal branch of the superior laryngeal nerve, is the fourth arch derivative, which is the key distractor here.

Reference: Langman's Medical Embryology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.