Fig. 4
From: Avian eggshell biomineralization: an update on its structure, mineralogy and protein tool kit
Comprehensive model for calcium and carbonate transport to the uterine fluid during eggshell calcification. The three potential pathways for ion transfer through uterine cells are transcellular, vesicular and paracellular mechanisms. They could function asynchronously or in an integrated fashion. The major protein players in each pathway are indicated on the figure (left). Graphical elements were from Servier Medical Art (https://smart.servier.com/), licensed under a Creative Commons Attribution 3.0 Unported License. Adapted from [20,21,22,23,24,25]