Hearing - Outer Ear Development
Introduction
The external ear is derived from 6 surface hillocks (auricular hillocks), three on each of pharyngeal arch 1 and 2.
The external auditory meatus is derived from the 1st pharyngeal cleft.
Some Recent Findings
Pinna- Auricle
Embryonic External Ear
Images of the lateral view of the human embryonic head from week 5 (stage 14) through to week 8 (stage 23) showing development of the auricular hillocks that will form the external ear. The adult ear is also shown indicating the part of the ear that each hillock contributes.
- develops from six aural hillocks: 3 on first pharyngeal arch and 3 on the second pharyngeal arch.
- originally on neck, moves cranially during mandible development
Pharyngeal Arch | Hillock | Auricle Component |
Arch 1 | 1 | tragus |
2 | helix | |
3 | cymba concha | |
Arch 2 | 4 | concha |
5 | antihelix | |
6 | antitragus |
- Outer- external auditory meatus
- derived from first pharyngeal cleft
- ectodermal diverticulum
- week 5 - extends inwards to pharynx
- until week 18 has ectodermal plug - plug forms stratified squamous epithelia of canal and outer eardrum
Embryonic period | Ectodermal cells proliferate and fill the entire lumen forming a meatal plug |
10 weeks | Meatal plug extends in a disc-like fashion. In the horizontal plane the meatus is boot-shaped with a narrow neck and the sole of the meatal plug spreading widely to form the future tympanic membrane medially. Proximal portion of the neck starts to be resorbed. |
13 weeks | Disc-like plug innermost surface in contact with the primordial malleus, contributes to the formation of the tympanic membrane. |
16.5 week | Meatus is fully patent throughout its length, lumen is still narrow and curved. |
18 week | Meatus is already fully expanded to its complete form. |
(Nishimura, 1992}
External Auditory Meatus
External auditory meatus and the outer ear.
Molecular
Outer Ear Genes
- controlled by genes that regulate arch 1 and 2 development
- related to hindbrain segmentation (rhombomere 4)
- Mouse - Hox a1/Hoxb1, goosecoid, Endothelin1, dHAND
Abnormalities
Microtia (autosomal-recessive) - A mutation in HOXA2[1]
References
- ↑ <pubmed>18394579</pubmed>
Reviews
Articles
Search PubMed
May 2010 "Outer Ear Development" All (1478) Review (120) Free Full Text (215)
Search Pubmed: Outer Ear Development Pinna Development
External Links
- Neuroscience Neuroscience - The External Ear
Glossary Links
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Cite this page: Hill, M.A. (2024, June 20) Embryology Hearing - Outer Ear Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Hearing_-_Outer_Ear_Development
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G