Table 2.

A schematic view of the functional roles of the allantoic epithelium.

Functions	Sites and mechanisms	Molecular components	References
Ion and H2O reabsorption from the allantoic fluid	Allantoic epithelial cells		[7, 14, 93]
Proton secretion towards the allantoic fluid and bicarbonate reabsorption	Mitochondria-rich cells	Vacuolar H+-ATPase	[21]
		Carbonic anhydrase	[21, 28]
		AE1 anion exchanger	[30]
Defence against luminal toxic contents	Granule-rich cells-secretion	Glycoconjugates rich in sialic acid and α-fucose residues	[29]