First and second branchial arch derivatives vs Third, fourth, and sixth branchial arch derivatives
How to tell First and second branchial arch derivatives and Third, fourth, and sixth branchial arch derivatives apart when a board question makes them look alike.
First is mastication/CN V; second is facial expression/CN VII; third is stylopharyngeus/CN IX; fourth/sixth are laryngeal/pharyngeal/CN X.
Side by side
First arch forms muscles of mastication, malleus/incus, maxillary/mandibular structures, and CN V innervation; second arch forms facial expression muscles, stapes, styloid, hyoid part, and CN VII.
Third arch forms stylopharyngeus/CN IX and thymus/parathyroid pouch relationships; fourth/sixth arches form pharyngeal/laryngeal muscles with CN X branches.
First arch forms muscles of mastication, malleus/incus, maxillary/mandibular structures, and CN V innervation; second arch forms facial expression muscles, stapes, styloid, hyoid part, and CN VII.
Third arch forms stylopharyngeus/CN IX and thymus/parathyroid pouch relationships; fourth/sixth arches form pharyngeal/laryngeal muscles with CN X branches.
The repair move
Before naming the answer, force the stem through the separator: First is mastication/CN V; second is facial expression/CN VII; third is stylopharyngeus/CN IX; fourth/sixth are laryngeal/pharyngeal/CN X.
Try a free question
CoreA medical student is studying branchial arch derivatives. The first branchial arch gives rise to muscles of mastication, the malleus and incus, the mandible, maxilla, and Meckel cartilage, and is innervated by which cranial nerve?
Show answer and explanation
Answer: A. CN V. First branchial arch derivatives (Meckel cartilage; CN V): muscles of mastication (masseter, temporalis, pterygoids), anterior 2/3 of tongue (somatic component), malleus and incus, sphenomandibular ligament, anterior digastric, mylohyoid, tensor tympani, tensor veli palatini. Innervated by CN V2 (maxillary) and V3 (mandibular).
Why the other choices are tempting
- B. CN VII innervates SECOND arch derivatives (facial expression muscles, stapes, styloid, etc.).
- C. CN IX innervates THIRD arch derivatives (stylopharyngeus).
- D. CN X innervates FOURTH and SIXTH arch derivatives (pharyngeal/laryngeal muscles).
- E. CN XI is associated with the postbranchial trunk muscles.
Flashcards
Tap a card to flip it.
What clue supports First and second branchial arch derivatives?
Choose First and second branchial arch derivatives when the stem gives this pattern: First arch forms muscles of mastication, malleus/incus, maxillary/mandibular structures, and CN V innervation; second arch forms facial expression muscles, stapes, styloid, hyoid part, and CN VII.
What clue supports Third, fourth, and sixth branchial arch derivatives?
Choose Third, fourth, and sixth branchial arch derivatives when the stem gives this contrasting pattern: Third arch forms stylopharyngeus/CN IX and thymus/parathyroid pouch relationships; fourth/sixth arches form pharyngeal/laryngeal muscles with CN X branches.
Quick answers
What is the fastest way to tell First and second branchial arch derivatives from Third, fourth, and sixth branchial arch derivatives?
First is mastication/CN V; second is facial expression/CN VII; third is stylopharyngeus/CN IX; fourth/sixth are laryngeal/pharyngeal/CN X.
What is the key clue for First and second branchial arch derivatives?
First arch forms muscles of mastication, malleus/incus, maxillary/mandibular structures, and CN V innervation; second arch forms facial expression muscles, stapes, styloid, hyoid part, and CN VII.
What is the key clue for Third, fourth, and sixth branchial arch derivatives?
Third arch forms stylopharyngeus/CN IX and thymus/parathyroid pouch relationships; fourth/sixth arches form pharyngeal/laryngeal muscles with CN X branches.