Dr. Matthew Mason: Further Information...
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Burford, C.M. & Mason, M.J. (2016) Early development of the malleus and incus in humans. Journal of Anatomy 229: 857-870.
There are two major theories in the literature regarding the developmental origins of the malleus and incus in human ears. The "classical interpretation" holds that both ossicles are essentially first pharyngeal arch structures (except for part of the anterior process and orbicular apophysis of the malleus). This interpretation is widely accepted by developmental biologists based on recent, molecular studies of mice. What we call the "dual arch interpretation" holds that the manubrium of the malleus and the long process of the incus are actually second-arch structures. This interpretation came from histological studies of human embryos in the 1960s but has been backed up by more recent work since then. This is the most popular interpretation in the human clinical literature, being used in the aetiological interpretation of human congenital abormalities which affect hearing. In this study, we looked at slides of human embryos in order to reassess the evidence for the "dual arch interpretation". It proved to be very difficult to determine the pharyngeal arch origins of the ossicles at the mesenchymal stages of development. Overall, we conclude that there is little clear support for the "dual arch interpretation", and we therefore feel that the "classical interpretation" is likely to be correct.
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