Pharyngeal Arches

Pharyngeal Arches

1. Arch 1

   • Forms on day 22
   • Mesenchyme
     • Rhombencephalon 2
       • Cranial neural crest
   • Meckel's cartilage
     • Intramembranous ossification
     • Dorsal end
       • Malleus and incus
     • Almost disappears
     • Fibrous remnant
       • Sphenomandibular ligament
   • Innervation
     • Trigeminal (V)
   • Pouch
     • Tubotympanic recess
       • Auditory tube
       • Tympanic cavity of middle ear
   • Auricular hillocks
   • Artery
     • Lost but contributes to the maxillary artery
       • Terminal external carotid

2. Arch 2

   • Forms on day 24
   • Mesenchyme
     • Rhombencephalon 4
       • Cranial Neural crest
   • Reichert's cartilage
     • Endochondial ossification
     • Stapes
     • Styloid process
     • Stylohyoid ligament
     • Superior part of hyoid bone
   • Innervation
     • Facial (VII)
   • Pouch
     • Obliterated by palatine tonsil
     • Forms MALT of tonsil epithelium
   • Auricular hillocks
   • Artery
     • Lost but forms stapedial artery in foetus

3. Arch 3

   • Forms on day 24
   • Mesenchyme
     • Rhombencephalon 6+7
       • Cranial neural crest
   • Cartilage
     • Inferior part of hyoid bone
   • Innervation
     • Glossopharyngeal (IX)
   • Pouch
     • Dorsal
       • Inferior parathyroid gland
     • Ventral
       • Thymus
   • Artery
     • Part of carotids

4. Arch 4

   • Forms on day 24
   • Mesnechyme
     • Cranial and occipital somites, prechordal mesoderm
   • Cartilage
     • Cartilage of the larynx
       • Thyroid
       • Cricoid
   • Innervation
     • Vagus (X)
   • Pouch
     • Dorsal
       • Ultimobrachial bodies
   • Artery
     • Left
       • Aortic arch
     • Right
       • Subclavian

5. Arch 5

   • DOES NOT EXIST

6. Arch 6

   • Forms on day 29
   • Mesenchyme
     • Cranial and occipital somites, prechordal mesoderm
   • Cartilage
     • Cartilage of larynx
       • Thyroid
       • Cricoid
   • Innervation
     • Vagus (X)
   • Artery
     • Pulmonary arteries
     • Ductus arteriosus on left