Which pharyngeal clefts persist into adulthood?

• A. All pharyngeal clefts persist into adulthood
• B. Only the 2nd pharyngeal cleft persists
• C. Only the 3rd pharyngeal cleft persists
• D. Only the 1st pharyngeal cleft persists

Answer: (D)

Only the first pharyngeal cleft persists into adulthood. The clefts are external grooves between the pharyngeal arches, and the first cleft remains to form the external auditory canal (ear canal). The other clefts are normally obliterated as development proceeds: the second arch overgrows the others and creates a temporary cavity called the cervical sinus, which then disappears. If those clefts fail to involute, remnants can form cysts or fistulas in the neck, but in typical development they do not persist. Thus, the first cleft is the one that remains in the adult.