Neuro: Pharyngeal Arches

Question 1

1st Pharyngeal Arch

Mandibular Arch

Answer 1

• Meckel’s cartilage –> Malleus and Incus and Maxilla
• Zygomatiic and Temporal squama
• Mandible
• Forms muscles of mastication and Mylohyoid, Digastric anterior belly, Tensor veli palatini, and Tensor Tympani muscles (innervated by CN V (V2 and V3)

Question 2

2nd Pharyngeal Arch

Hyoid Arch

Answer 2

• Reichert’s cartilage
• Develops the Stapes, Styloid process, Lesser Cornu, and Upper half of the Hyoid bone
• Muscles of Facial expression and Digastric Posterior belly, Sylohyoid, and Stapedius muscles –> which are innervated by CN VII

Question 3

3rd Pharyngeal Arch

Answer 3

• Forms the Greater cornu and Lower half of the Hyoid bone
• Forms the Stylopharyngeus muscle, which is innervated by CN IX

Question 4

4th Pharyngeal Arch

Answer 4

• Laryngeal Cartilages
• Forms the muscles of the Soft palate (CN X) except the Tensor veli palatini (CN V)
• Forms the muscles of the Pharynx (CN X) except Stylopharyngeus (CN IX)
• Forms the Cricopharyngeus muscle (CN X)
• All innervations by CN X are by the Superior Laryngeal branch

Question 5

6th Pharyngeal Arch

Answer 5

• Laryngeal cartilages
• Forms the Intrinsic muscles of the Larynx, except the Cricothyroid
• Forms the Upper muscles of the Esophagus
• All are innervated by CN X - Laryngeal branch

Question 6

Pharyngeal Pouch 1

Answer 6

• Endoderm
• Forms the Epithelium of the Auditory tube and the Middle ear cavity

Question 7

Pharyngeal Pouch 2

Answer 7

• Endoderm
• Forms the Epithelium and Crypts of the Palantine tonsil

Question 8

Pharyngeal Pouch 3

Answer 8

• Endoderm
• Forms the Inferior Parathyroid gland and Thymus

Question 9

Pharyngeal Pouch 4

Answer 9

• Endoderm
• Forms the Superior Parathyroid gland and Ultimobranchial body

Question 10

Pharyngeal Groove 1

Answer 10

• Ectoderm
• Gives rise to the Epithelium of the External Auditory meatus and Skin over the Tympanic membrane

Question 11

Pharyngeal Grooves 2, 3, and 4

Answer 11

• Ectoderm
• Are Obliterated

Question 12

Pharyngeal Membrane 1

Answer 12

• Located at the junction of each Pharyngeal Groove and Pouch
• Gives rise to the Tympanic membrane

Question 13

Pharyngeal Membranes 2, 3, and 4

Answer 13

• Are Obliterated