It was once thought that the middle ear was made from endodermal cells, but the Department of Craniofacial Development at King’s College London’s Dental Institute has found that it’s not.
It is actually made up of endodermal and neural crest cells. This discovery may be the reason behind a common childhood ear infection called glue ear (a type of otitis media called secretory otitis media, or SOM). The lining that originates from the endodermal cells are covered in cilia (hairs) which help clean debris from the ear. Neural crest cells don’t have cilia, leaving them prone to infection.
Also, mammals are rather unique in that we have three middle ear bones; reptiles and birds only have one. Mammals have consequently evolved to create an air-filled space to house these extra bones. There might, therefore, be a link between the development of 3 middle ear bones and the development of two types of middle ear cells…an evolutionary glitch! Textbooks may even need to be re-written because of this breakthrough.
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