Title
Postnatal development of the middle ear in New Zealand white rabbits : ossicles and tympanic ring Postnatal development of the middle ear in New Zealand white rabbits : ossicles and tympanic ring
Author
Faculty/Department
Faculty of Sciences. Physics
Publication type
article
Publication
Amsterdam ,
Subject
Physics
Biology
Human medicine
Source (journal)
Hearing research. - Amsterdam
Volume/pages
272(2011) :1/2 , p. 148-156
ISSN
0378-5955
ISI
000288418100016
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
We studied the postnatal development of the middle ear (ME) in New Zealand White rabbits. Bullae were scanned using a desktop X-ray microtomograph and 3D models of the ME ossicles as well as the tympanic ring (TR) were prepared. In 0, 1, 2 days old rabbits the ossification process was incomplete. We can therefore present quantitative data obtained from older rabbits (ages: 4180 days) and a qualitative description at the earlier ages. For a number of the measured parameters an exponential curve could be fitted to the data, and the time constant (at which 63% of the final value was obtained) was calculated. The length of the manubrium increased rapidly in a period of about 15 postnatal days, from 1.73 mm to 4.08 mm. The distance between the tip of the malleus and the TR increased rapidly until day 30, from nearly 0 to 1.40 mm. The increase of the surface area within the TR was small as compared to inter-specimen variance, but the ratio [tympanic membrane area]/[TR area] clearly increased (from 1.00 to 1.11), with a time constant of 8.3 days. The area of the stapes footplate (FP) increased rapidly in about 15 days (from 0.72 mm2 to 1.49 mm2, time constant 4.8 days). The TR was nearly developed at birth whereas the stapes footplate was quite underdeveloped. The distance between the tip of the malleus and the incudomallear rotation axis increased rapidly until day 20 and varied between 3.47 mm and 5.00 mm. The distance between the tip of the incus and the rotation axis increased until day 133, from 1.39 mm to 1.69 mm. Our study shows that in rabbits the ME is underdeveloped at birth and that the functional geometry develops over the same time course as the ability to hear. The conical shape of the tympanic membrane (TM) is formed by retraction and growth of the manubrium, mainly during the first 40 days after birth.
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