Fetal development and variations in the cartilages surrounding the human external acoustic meatus

Yasutoyo Ikari, Yukio Katori, Aiji Ohtsuka, Jose Francisco Rodríguez-Vázquez, Hiroshi Abe, Tetsuaki Kawase, Gen Murakami, Shin ichi Abe

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5 Citations (Scopus)

Abstract

In contrast to the osseus part that develops from the tympanic ring of the squamous part of the temporal bone after birth, there is little information on fetal development of the cartilages surrounding the human external acoustic meatus. Using routine histology and immunohistochemistry, we examine sections of 22 fetuses (CRL 100-270. mm) to study the development of these cartilages. Early external ear cartilages are composed of three groups: (1) a ring-like cartilage at the putative tragus on the anterior side of the meatus, (2) two or three bar-like cartilages along the inferior wall of the meatus, and (3) a plate-like cartilage in a skin fold for the putative helix on the posterior side. In contrast to the first and second pharyngeal arch cartilages, all the external ear cartilages express glial fibrillary acidic protein. Notably, the bar-like cartilages along the meatus are connected with a fascia-like structure to the second pharyngeal arch cartilage. Later, with considerable individual variation, new cartilage bars extend from the inferior cartilages to the superior side of the meatus. Thus, via an intermediate stage showing a chain of triangular elastic cartilages, a chain of bar-like cartilages on the inferior side appears to change into a complex of H-shaped cartilages. Numerous ceruminous glands are seen in the thick subcutaneous tissue overlying the cartilaginous part of the meatus. However, they do not insert into the cartilage. The external ear cartilages develop much earlier than, and independently of, the osseus part.

Original languageEnglish
Pages (from-to)128-136
Number of pages9
JournalAnnals of Anatomy
Volume195
Issue number2
DOIs
Publication statusPublished - Mar 2013

Keywords

  • Cartilage
  • External acoustic meatus
  • Human fetuses
  • Temporal bone
  • Tragus
  • Tympanic ring

ASJC Scopus subject areas

  • Anatomy
  • Developmental Biology

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  • Cite this

    Ikari, Y., Katori, Y., Ohtsuka, A., Rodríguez-Vázquez, J. F., Abe, H., Kawase, T., Murakami, G., & Abe, S. I. (2013). Fetal development and variations in the cartilages surrounding the human external acoustic meatus. Annals of Anatomy, 195(2), 128-136. https://doi.org/10.1016/j.aanat.2012.07.009