Which structures contribute to the cervical sinus?

Which structures contribute to the cervical sinus?

• A. Second, third, and fourth pharyngeal arches
• B. First pharyngeal arch
• C. Second pharyngeal clefts
• D. Oral ectoderm vesicles

Answer: (A)

The cervical sinus forms as a result of the second pharyngeal arch growing caudally and overgrowing the third and fourth arches. This overgrowth creates a temporary cavity between the second arch and the underlying third and fourth arches that opens to the exterior of the neck. Normally this sinus is obliterated as development proceeds. So, the structures that contribute to the cervical sinus are the second, third, and fourth pharyngeal arches, since their arrangement and interactions create that transient space. The first arch doesn’t participate in forming this sinus, the external grooves (clefts) are largely covered by the second arch’s overgrowth, and oral ectoderm vesicles are not involved in creating the cervical sinus.

The cervical sinus forms as a result of the second pharyngeal arch growing caudally and overgrowing the third and fourth arches. This overgrowth creates a temporary cavity between the second arch and the underlying third and fourth arches that opens to the exterior of the neck. Normally this sinus is obliterated as development proceeds. So, the structures that contribute to the cervical sinus are the second, third, and fourth pharyngeal arches, since their arrangement and interactions create that transient space. The first arch doesn’t participate in forming this sinus, the external grooves (clefts) are largely covered by the second arch’s overgrowth, and oral ectoderm vesicles are not involved in creating the cervical sinus.