Hearing - Outer Ear Development
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.
The postnatal human external ear structure also selectively boosts frequencies around 3 kHz, by a sound pressure level of 30 to 100-fold, that correspond to frequencies associated with speech. The anatomical position, on either side of the head, also allows exquisite localization of sounds in space by neural comparison of signals reaching each ear.
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Some Recent Findings
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
Movement of the external ear in human embryo (week 6 to 8)
|Pharyngeal Arch||Hillock||Auricle Component|
- 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.|
Based on data from
| Image shows the embryonic and fetal growth of the auricular cartilage within the pinna.
Fig. 6. Lateral views of left auricular cartilage, taken from reconstructions of human embryos of the Carnegie Collection: No. 460 (21 mm.), No. 417 (32 mm.), No. 886 (43 mm.). X14.
Human Auricle Development
External Auditory Meatus
External auditory meatus and the outer ear.
The auriculotemporal nerve supplies a large part of the pinna, some innervation may also arise from the trigeminus.
Postnatally, human ears continue to grow throughout the entire lifetime and have a sexually dimorphic pattern, described in a large study. Three anatomical features of the ear were found to not grow at all after birth; Concha auriculae width, Incisura intertragica width, and the helical brim diameter of the auricle.
- birth - external ear bigger than the large head in proportion to the body
- childhood - large yearly increases decrease by 8 or 10 years of age.
- adult - male increases in all parameters were greater than for female ears.
|Birth||52 (4.3)||52 (4.1)|
|20 yrs||61 (3.9)||65 (4.0)|
|Older than 70 yrs||72 (4.6)||78 (4.8)|
- Darwin's tubercle - (Woolnerian tip) is a tubercle is seen along the upper, posterior portion of the helix (upper and middle thirds).
- "railroad track" - associated with fatal alcohol syndrome, the curve at top part of outer ear is underdeveloped and folded over parallel to curve beneath.
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
There are a range of external ear abnormalities relate to final structure, size and position. In some cases these abnormalities relate directly to pharyngeal arch development or may be part of a wider spectrum of abnormalities associated with a genetic or environmental (fetal alcohol syndrome) disorders. Some known abnormalities include: anotia, microtia, prominent ear, lop ear, cup ear, cryptotia and Stahl's ear. Other associated external ear abnormalities include the formation of the external auditory meatus (canal) and pre-auricular fistulae (pits) and appendages. Finally, a range of abnormalities can be found associated with the overlying skin of both the external ear and the ear canal.
Minor structural anomalies have been shown to be corrected by appropriate splinting in the early neonatal period.
Upper Auricular Detachment
Microtia (autosomal-recessive) - A mutation in HOXA2
Oculo-auricular syndrome - A mutation in the NKX5-3 human homeobox gene.
A rare ear abnormality, where the rim of the ear is flattened and the upper portions deformed. More common in Oriental background and can occur from mild to severe. The skin and cartilage are both folded to different degrees that can result in a pointed upper edge. This pointed ear has been said to resemble the Star Trek television character "Vulcan" ear shape.
External Auditory Meatus
The external auditory meatus (canal) can also fail to canalise leading to a range of malformation including membranous and/or bony atresia and stenosis.
External Auditory Meatus Stenosis
- Type A - a marked narrowing of the canal with an intact skin layer.
- Type B - a partial development of the canal with an atresia plate at the medial part.
- Type C - a complete bony canal atresia.
Pre-auricular Fistulae and Appendages
There are also a range of pre-auricular fistulae (pits) and appendages that generally occur in a specific region beside the tragus and crus helicis.
Posterior helix pit associated with Beckwith-Wiedemann syndrome.
- ↑ 1.0 1.1 Miho Kagurasho, Shigehito Yamada, Chigako Uwabe, Katsumi Kose, Tetsuya Takakuwa Movement of the external ear in human embryo. Head Face Med: 2012, 8();2 PMID:22296782 | PMC3286420 | Head Face Med.
- ↑ Chiarella Sforza, Gaia Grandi, Miriam Binelli, Davide G Tommasi, Riccardo Rosati, Virgilio F Ferrario Age- and sex-related changes in the normal human ear. Forensic Sci. Int.: 2009, 187(1-3);110.e1-7 PMID:19356871
- ↑ Y Nishimura, T Kumoi The embryologic development of the human external auditory meatus. Preliminary report. Acta Otolaryngol.: 1992, 112(3);496-503 PMID:1441991
- ↑ George L. Streeter Development of the auricle in the human embryo Carnegie Institution No.69 111-138 (1922).
- ↑ 5.0 5.1 Carsten Niemitz, Maike Nibbrig, Vanessa Zacher Human ears grow throughout the entire lifetime according to complicated and sexually dimorphic patterns--conclusions from a cross-sectional analysis. Anthropol Anz: 2007, 65(4);391-413 PMID:18196763
- ↑ Michael Sand, Daniel Sand, Dominik Brors, Peter Altmeyer, Benno Mann, Falk G Bechara Cutaneous lesions of the external ear. Head Face Med: 2008, 4();2 PMID:18261212 | PMC2267455 | Head Face Med.
- ↑ Fabrizio Schonauer, Ivan La Rusca, Guido Molea Non-surgical correction of deformational auricular anomalies. J Plast Reconstr Aesthet Surg: 2009, 62(7);876-83 PMID:18490209
- ↑ Fatemeh Alasti, Abdorrahim Sadeghi, Mohammad Hossein Sanati, Mohammad Farhadi, Elliot Stollar, Thomas Somers, Guy Van Camp A mutation in HOXA2 is responsible for autosomal-recessive microtia in an Iranian family. Am. J. Hum. Genet.: 2008, 82(4);982-91 PMID:18394579
- ↑ Daniel F Schorderet, Olivia Nichini, Gaëlle Boisset, Bozena Polok, Leila Tiab, Hélène Mayeur, Bahija Raji, Gauillaume de la Houssaye, Marc M Abitbol, Francis L Munier Mutation in the human homeobox gene NKX5-3 causes an oculo-auricular syndrome. Am. J. Hum. Genet.: 2008, 82(5);1178-84 PMID:18423520 | PMC2427260
- ↑ S Kösling, M Omenzetter, S Bartel-Friedrich Congenital malformations of the external and middle ear. Eur J Radiol: 2009, 69(2);269-79 PMID:18054456
F Alasti, G Van Camp Genetics of microtia and associated syndromes. J. Med. Genet.: 2009, 46(6);361-9 PMID:19293168
Elena Torban, Paul Goodyer The kidney and ear: emerging parallel functions. Annu. Rev. Med.: 2009, 60();339-53 PMID:18976115
F Wood-Jones, W I-Chuan The Development of the External Ear. J. Anat.: 1934, 68(Pt 4);525-33 PMID:17104502
Chiarella Sforza, Gaia Grandi, Miriam Binelli, Davide G Tommasi, Riccardo Rosati, Virgilio F Ferrario Age- and sex-related changes in the normal human ear. Forensic Sci. Int.: 2009, 187(1-3);110.e1-7 PMID:19356871
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Cite this page: Hill, M.A. (2013) Hearing - Outer Ear Development. Retrieved December 4, 2013, from http://embryology.med.unsw.edu.au/embryology/index.php?title=Hearing_-_Outer_Ear_Development
- Dr Mark Hill 2013, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G