Endosalpinx is the inner mucosal layer of the Fallopian tube responsible for transporting gametes and embryos and tubal fluid secretions. The endosalpinx is composed of epithelial cells and the lamina propria mucosa; the latter is a network of connective tissue with a mixed cell population. The epithelial tissue on the inner surface of the Fallopian tube is made up of two main cell types: ciliated epithelial cells and nonciliated secretory epithelial cells. Beneath the lining of epithelium is the lamina propria, which consists of fibroblast, immune, and progenitor cells. Mucosal layer forms dense internal folds, increasing the surface area of epithelial cell lining to achieve high fluid secretory rate.

Multiciliated epithelial cells in the Fallopian tube are featured with a classical 9 + 2 microtubule structure (axoneme) to create a beating movement (Lodish et al., 2000). The movement of axoneme requires adenosine triphosphate (ATP) as the energy source. Elevated E2 concentration stimulates ATP production at the apical surface of the epithelial cells and results in an increase in ciliary beat frequency. In rabbits, the absence of calcium results in nonbeating cilium. This suggests the mechanism involves a calcium-dependent ciliary regulation (Verdugo, 1980), potentially through a voltage-gated calcium channel (Doerner et al., 2015).