Which arch forms the stapedius muscle and auricular muscles?

Which arch forms the stapedius muscle and auricular muscles?

• A. First pharyngeal arch
• B. Second pharyngeal arch
• C. Third pharyngeal arch
• D. Fourth pharyngeal arch

Answer: (B)

Muscle derivatives of the pharyngeal arches follow specific patterns, so identifying which arch gives a particular muscle helps map development. The second pharyngeal arch, also known as the hyoid arch, is responsible for several small neck and ear muscles, including the stapedius of the middle ear and the various auricular muscles around the ear. These muscles share a common origin in mesenchyme of that arch and are innervated by the facial nerve, which is a helpful clue linking them to the second arch. In contrast, the first arch forms muscles mainly of mastication (and a few others like mylohyoid); the third arch contributes stylopharyngeus; and the fourth arch gives rise to other pharyngeal muscles and the cricothyroid. So the stapedius and auricular muscles come from the second arch.

Muscle derivatives of the pharyngeal arches follow specific patterns, so identifying which arch gives a particular muscle helps map development. The second pharyngeal arch, also known as the hyoid arch, is responsible for several small neck and ear muscles, including the stapedius of the middle ear and the various auricular muscles around the ear. These muscles share a common origin in mesenchyme of that arch and are innervated by the facial nerve, which is a helpful clue linking them to the second arch.

In contrast, the first arch forms muscles mainly of mastication (and a few others like mylohyoid); the third arch contributes stylopharyngeus; and the fourth arch gives rise to other pharyngeal muscles and the cricothyroid. So the stapedius and auricular muscles come from the second arch.