The formation of the primitive choanae and the junction of the primary and secondary palates in the mouse

Abstract

This study has followed the development of the primary choanae in the mouse and has shown that they originate at the developmentally strategic position of junction between the primordia of the primary and secondary palates and that this basic anatomic relationship is maintained throughout further development. Involution of the oronasal membrane begins late in the 11th day (stage 19) with the formation of interstitial gaps. The gaps enlarge and coalesce so that a completely patent opening between nasal passage and stomodeum is established by 13 days (stage 21). The membrane consists of two layers of simple squamous epithelium which become separated as involution progresses. The form of the choanal antrum changes from a simple funnel-shaped ellipse early in the 13th day to a complex slitlike opening within the following 24 hours. This coincides with the completion of a definitive primary palate and the enlargement and elevation of the shelves of the secondary palate. The maturation of the incisive papilla and interchoanal columella is related to the final stages of choanal morphogenesis. Thus, by stage 22 (14 days) the shape of the primary choanae and their anatomic relationship to the primary and secondary palates are established, and they remain essentially unchanged in later stages.

Signaling integration in the rugae growth zone directs sequential SHH signaling center formation during the rostral outgrowth of the palate

“…3A, D). Choanae are bilateral involutions that will form the nasal cavity and provide landmarks for the junction between the primary and secondary palate (Tamarin, 1982). At E11.5, the mesenchymal expression of Barx1 extends nearly along the entire length of the palatal shelf and abuts the posterior limit of the primary choanae (Fig.…”

“…3C and F). During the initial stages of secondary palate development, the site of R1 formation is closely associated with the formation of the primary choanae that presages the site of fusion between the primary palate with the anterior secondary palate (Tamarin, 1982). Therefore, growth of the anterior hard palate occurs via the expansion of the domain intervening the FEZ and R1.…”

Palatal shelf movement during palatogenesis: a fate map of the fetal mouse palate cultured in vitro

“…It has been shown that the forcing of palatal shelves upward by the tongue is not a necessary prerequisite for shelf elevation and that shelf elevation is an active process which can be attained even in the absence of the tongue (Brinkley et al 1974;Walker and Patterson 1974;Wee et al 1976;Zimmerman et al 1983;Shiota et al 1990b); therefore, our culture condition where the lower jaw and tongue are removed does not underestimate the role of the tongue in palatal elevation. Although the primary palate and the nasal septum were suggested to participate in palatal closure (Tamarin 1982), their contribution seems to be limited at least in the initial steps of secondary palate fusion in vitro (Shiota et al 1990b).…”

Relationship of the Primary Choanae and Anterior Cranial Base in the Mouse Embryo

“…Previous studies have described the topographical development of the primary choanae in the mouse [Pourtois. 1972;Tamarin. 1982;Sim.…”

“…The pattern of growth of the primary choanae has received little attention. The topographical development of the primary choanae has been described in the mouse [Tamarin, 1982: Sim. 1985].…”