How do baby birds get oxygen inside the eggs?

Image credit: hobbyfarms.com

Have you ever seen an egg, it has no place for the air to go inside, so how the birds breathe inside the egg? Do they breathe? 

Let's know, 

Birds eggs which are hard-shelled contain albumen (egg white) and a yolk. The fertilized egg cell, or embryo, develops within the yolk and feeds off of it and the white. The baby bird inside the egg has everything shelter, food, almost everything it needs, except a little fresh air. 

A bird in the egg or other reptile doesn't have as obvious way to inhale and exhale, but how that is possible in the egg? 

Answer to this question is that, the egg's shell has two membranes just below it. When the eggs are laid by the mother, they are very warm and as they cool the material inside it gets shrink a little. Then the two membranes pull apart a little and create a small pocket or sack of air. 

As the bird grows, it breathes in oxygen from the air sack and exhales carbon dioxide. Several thousand microscopic pores are present over the egg's surface and allow the co2 to escape and fresh air to get in. 

These pores allow some moisture to get into the egg to keep developing bird and egg parts from drying out. 

This how the baby birds breathe inside the egg. 

Comment your questions which you want to be answered.