anterior midgut primordium [FBbt_00000444]

anterior midgut primordium

ID: FBbt_00000444

The primordium that will develop into the anterior midgut of both larva and adult. This forms during stage 8 when anterior endoderm cells, which have invaginated at the anterior end of the ventral furrow, divide and undergo an epithelial-to-mesenchymal transition. During stage 9, its cells divide a second time. During stage 10, the primordium attaches to the internal end of the stomodeum and spreads posteriorly with the stomodeal invagination, splitting into two lobes extending on either side of the yolk sac. A separate group of cells fuse with this primordium during stage 11. These cells delaminate from the stomodeum, becoming mesenchymal and mingling with the existing cells of the primordium. Fate mapping suggests that these cells will form the anterior-most part of the midgut, including the gastric caeca (Technau and Campos-Ortega, 1985). Adult midgut progenitors separate from the primordium during late stage 11 and stage 12. The remaining cells reorganize to become epithelial plates which then begin to fuse with the posterior midgut primordium during stage 12, forming the fused midgut primordium.

This primordium may be temporally subdivided into the inclusive anterior midgut primordium, including adult midgut progenitors and the anterior midgut primordium proper, which contains only progenitors of the embryonic/larval midgut. However, the primordium proper exists only briefly during stage 12 and so we have chosen not to represent it in this ontology. Please use 'anterior midgut primordium' for both cases. Note, there is some controversy surrounding the account of anterior midgut development given in this definition. See Foe, 1989 and notes on this paper in Campos-Ortega and Hartenstein, 1997, pg 151-152).