Histological development of stapes footplate in human embryos.

Normal development of the human stapes footplate was investigated in serial sections by light microscopy. Materials were obtained from 35 Japanese embryos from the 6th to 32nd week of embryonal age. Eighteen embryos up to 16 weeks of age (3.5mm to 105mm in crown-rump length) were examined, focusing particularly on the lamina stapedialis of the otic capsule. The present study showed that primordial formation of the lamina stapedialis appeared in 16mm embryo and that the lamina was completely formed and fused to the base of the annular stapes in a 35mm embryo. In a 50mm embryo, the adult form of stapes was found with a rim and annular ligament. The results, therefore, seemed to essentially agree with the theory of dual origin and development of the footplate proposed by Cauldwell and Anson, and teratogenic agents might affect any stage of the process producing anomalies, including congenital footplate fixation, congenital absence of the oval window and calcification of the annular ligament.