Figure 5: Transmission electron microscopy on generated tubules after 13 days of culture (a-i). Surface view demonstrates that tubules contain a polarized epithelium with isoprismatic cells. At the border between the luminal and lateral plasma membrane in all of the series a tight junctional complex is developed (arrow head). The basal side of the epithelium rests on a basal lamina (asterisk) (a-c). The tight junctional complex consists of a zonula occludens (ZO), zonula adhaerens (ZA), and a desmosome (D) (d-f). At the basal aspect a continously developed basal lamina (asterisk) can be observed (g-i).