What is inside a bird egg?

What is inside a bird egg?

An egg is made of several elements, such as a shell, two shell membranes (inner and outer membranes), a vitelline membrane, an air chamber, the chalazae, the egg white (called albumen), the yellow egg yolk, and a germinal disc.  

The shell is hard and can easily break. About 95% of the shell is made of minerals.

The two shell membranes include a thin inner membrane and a thin outer membrane. Both are situated between the hard shell and the egg white. The outer membrane is connected to the shell and the inner membrane is around the egg white.

The vitelline membrane is a thin layer around the egg yolk.

An air chamber is the space that forms after the egg is laid. 

The chalazae are two cords, like string, that keep the yellow egg yolk in place. 

The egg white (albumen) is clear liquid around the yellow egg yolk. It is two-thirds (66%) of the whole egg and consists of 87% water and 13% albumen. It protects the yellow egg yolk. It turns white when the egg is cooked.

The yellow egg yolk is one third (33%) of the whole egg and is made of 50% water, 15% protein, and 35% lipids.

Inside the yellow egg yolk is a small white spot (or blood red spot) called the germinal disc. It is the seed (ovule) that holds the genetic material that determines what the bird will look like.

hard shell and the two shell membranes
hard shell and the two shell membranes
egg yolk, germinal disc, vitelline membrane, and albumen

Photographer: Martina Nicolls


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