Stapes, Fissula Ante Fenestram and Associated Structures in Man: Iii. From Embryos 6.7 to 50 Mm. In Length

Abstract

In earlier articles1 the major steps in the rapid embryologic development of the stapes and those in the slower alteration of postnatal specimens were described and illustrated, selected stages between 7\ m=1/ 2\ 2 weeks (22.8 mm.) and 70 years being utilized; the morphologic aspects of the closely related vestibular rim and fissular prolongation were considered at the same time. In the present phase of the investigation a more inclusive and numerically larger set of stages is being studied, ranging between that of the embryo 6.7 mm. in length and that of an adult aged 75 years. By this means, detailed information on the morphogenesis and increment will be added, and hiatuses in present knowledge of stapedial form will be closed.The current article will carry the stapedial history through stages at which the cartilage has assumed definitely stirrup-shaped form; subsequent articles will account separately for equally crucial morphogenetic epochs.

The origin of the stapes and relationship to the otic capsule and oval window

“…In humans, some histological studies have indicated that the stapes footplate is derived from the otic capsule (Cauldwell and Anson, 1942;Bast and Anson, 1949;Hanson et al, 1962;Masuda et al, 1978), while later studies report that the stapes has no mesoderm derivatives and develops independently from the otic capsule (Rodríguez-Vazquez, 2005). In mice, retinoic acid treatment has been shown to lead to formation of a complete stapes, at a distance from the otic capsule, indicating again an independent origin (Louryan et al, 2003).…”

Normal Development of the Ear and Its Mechanics

“…embryos (Cauldwell and Anson, 1942). It arises from the cranial end of the second visceral bar as a bulbous mass of mesenchyme and is wholly separate from the otocyst and the meager condensations of mesenchymal cells about the periphery of the otocyst.…”

“…The part of the labyrinthine capsule which comes into contact with the base of the stapes is called lamina stapedialis. Its outer parts atrophy while its inner parts fuse with the basal plate of the stapes and provide the stapedial rim, the vestibular surface of the base and the basal perichondrium, as well as the annular ligament of the definitive stapes (Cauldwell and Anson, 1942). All the other parts are derived from the second visceral bar.…”

“…The first anläge of the former structure was seen in 34 mm. embryos (Cauldwell and Anson, 1942), of the latter, in 100 mm. embryos.…”

The Ear in Severe Malformations of the Head: A Discussion of the Formal and Causal Genetic Factors Involved

“…10) Yntema, 1955 These findings are in agreement with the fact that in man the stapedial footplate has a dual origin. The stapedial rim, the vestibular surface, the basal perichondrium, and the annular ligament are derived from the lamina stapedialis of the labyrinthine cap¬ sule, the remainder of the footplate from the second visceral bar (Cauldwell and Anson, 1942).…”