Eggshell Texture and Structure
Eggshells of all Textures
|Cormorant eggs||Tinamou eggs|
Regardless of how smooth an egg may feel, all eggshells have tiny holes or
pores. The domestic hen's egg, for example, may have 7500 pores. Most
of these pores are at the blunt end of the egg. Pores connect the egg with
its surroundings. Respiratory gases as well as water vapour travel through
these channels and enable the egg to breathe.
Why an eggshell?
and Emu eggs
Eggshells are made of calcium and magnesium salts within a fibrous network. Calcite is the main salt used as building material for the shell. As the embryo develops, calcium is transferred from the shell to the growing bones of the embryo. After a chick hatches, the mother sometimes eats the shell to recover some of the calcium lost in the making of an egg.
The outer surface of the eggshell is covered by the cuticle. The cuticle is a thin layer made of proteins. The cuticle adds strength to the shell, gives the shell its texture and provides a barrier against bacteria.