Expansion
Arch one Meckel's begun, arch two Reichert's true, arch three hyoid's key, arch four six larynx fix
Mnemonic
Each arch gives a cartilage, and the first two give the ossicles:
- Arch 1 - Meckel’s cartilage: malleus and incus, sphenomandibular ligament, the mandible forming around it
- Arch 2 - Reichert’s cartilage: stapes, styloid process, stylohyoid ligament, lesser horn and upper hyoid
- Arch 3 - greater horn and lower body of the hyoid
- Arch 4 - thyroid cartilage, epiglottis
- Arch 6 - cricoid, arytenoid and remaining laryngeal cartilages
“1 and 2 make the ear bones, 2 and 3 make the hyoid, 4 and 6 make the larynx.”
The nerve supply follows the cartilage, which is why the stapedius is facial (arch 2) while tensor tympani is trigeminal (arch 1), despite both sitting in the middle ear.
Treacher Collins syndrome is a first arch disorder, giving mandibular and zygomatic hypoplasia, downslanting palpebral fissures and ear abnormalities.
Expansion
- Arch 1 - Meckel’s cartilage, forms malleus and incus
- Arch 2 - Reichert’s cartilage, forms stapes and styloid process
- Arch 3 - contributes to the greater horn and body of the hyoid
- Arch 4 and 6 - form the laryngeal cartilages