The Embryologic Development of the Human External Auditory Meatus

Abstract

During the final period of embryogenesis, a funnel-shaped tube continues medially into the mesenchymal tissue forming a curved path. Although this may sound simple, the development occurring during early fetal life is in fact very complex. At first, ectodermal cells proliferate to fill the lumen of the meatus, forming the meatal plug, and then at 10 weeks the bottom of the plug extends in a disc-like fashion, so that 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. At the same time, the plug in the proximal portion of the neck starts to be resorbed. In the 13-week fetus, the disc-like plug begins to show signs of its final destiny; the innermost surface of the plug in contact with the anlage of the malleus is ready to contribute to the formation of the tympanic membrane. In the 15-week fetus, the innermost portion of the disc-like plug splits, leaving a thin ectodermal cell layer of immature tympanic membrane. The neck of the boot forms the border between the primary and secondary meatus, and is the last part to split. In the 16.5-week fetus, the meatus is fully patent throughout its entire length, although the lumen is still narrow and curved. In the 18-week fetus, the meatus is already fully expanded to its complete form.

The development of the mammalian outer and middle ear

“… Data from Michaels & Soucek (); Nishimura & Kumoi (); Mallo & Gridley (); Miyake et al. (); Nishizaki et al.…”

“…Later this meatal plug opens to form the ear canal and surface of the tympanic membrane, at the same time cornification of the ectoderm‐derived stratified squamous epithelium occurs. Keratin squames can be seen in the forming cavity during this opening process (Michaels & Soucek, ; Nishimura & Kumoi, ; Nishizaki et al. ; Schoenwolf et al.…”

Programmed cell death in the development of the mouse external auditory canal

“…Morphogenesis of the external auditory canal (EAC) has generally been described as follows (Van De Water et al, 1988;Kenna, 1990;Nishimura and Kumoi, 1992;Larsen, 1993). At approximately the fourth gestational week (g.w.…”

Fluctuating Asymmetry and Sexual Orientation in Men and Women

“…On the other hand, the external ear has a more discrete developmental timetable. The pit that forms the primary external auditory canal appears during the sixth prenatal week and the cartilaginous meatus is completed by 18 weeks prenatal (Nishimura & Kumoi, 1992). Auricular width (from tragus to antihelix) is fixed by the first postnatal year with breadth development completed by age six; however, vertical auricular growth does not stop until 12 years of age (Kalcioglu, Miman, Toplu, Yankinci, & Ozturan, 2003).…”