Question

Nerves of the branchial arch are derived from:

• A. Mesoderm
• B. Endoderm
• C. Neural crest
• D. Neuroectoderm

Hint:

Peripheral neurons and glia of the arches are migratory crest cells.

Answer 1

The Correct Option is C

Step 1: Branchial (pharyngeal) arches are bars of mesoderm covered externally by ectoderm and lined internally by endoderm. Within each arch develop a cartilage bar, a muscle component, an aortic arch artery and a nerve.
Step 2: The neural and glial elements of the arches arise from neural crest cells. Neural crest cells are ectoderm-derived cells that delaminate from the margins of the neural tube and migrate widely. Cranial neural crest migrates into the pharyngeal arches and forms ectomesenchyme, neurons and glia. Therefore the nerves associated with the branchial arches are of neural crest origin.
Step 3: Why the others are wrong. Mesoderm forms the muscle and the core connective tissue of the arch, not the nerves. Endoderm lines the arches and forms pharyngeal pouch derivatives. Neuroectoderm forms the central nervous system; the peripheral arch neurons and their supporting cells come specifically from neural crest.