Air chamber
1 lime shell
2 shell skin
3 shell skin
4 chalaza (hail
cord ) 5 outer egg white (thin) 6 medium egg white (thick) 7 yolk skin 8 yolk 9 germ stain ("houndstooth") 10 yellow yolk 11 white yolk 12 inner egg white (thin ) 13 Chalaza (hail cord) 14 Air chamber
15 Cuticle
The air chamber of a bird's egg lies between the egg skin (shell skin) and the calcareous shell, always at the blunt end of the egg. It becomes larger as the contents of the membrane shrink. Water evaporates from the egg white through the egg membrane and the lime shell to the outside. The yellow yolk nourishes the chick , which partly assimilates the substances (grows from them) and partly metabolizes them . For this cellular respiration , oxygen is absorbed through the well-perfused egg membrane and water and carbon dioxide are released.
Shortly before hatching, the blood supply to the egg membrane decreases and the chick begins to breathe . Even if the membrane tears open towards the chamber, the air in it is quickly used up. The increasing carbon dioxide content triggers contractions of the neck muscles in the chick, causing the head to lift and the egg tooth to break through the shell.
In the household, the growth of the air chamber allows a rough determination of age: a fresh egg sinks to the bottom in water, an older one rises.