How does a chicken hatch?

Answer 1

If an egg does not meet a sperm cell in the oviduct it will still be laid by the hen. But the embryo will not develop because the egg has not been fertilized. A small white spot on the yolk will remain white. If, however, the egg has been fertilized this white spot will soon become red with blood as the embryo starts to develop. For a chicken, it takes 21 days from the time the egg is laid to the time the chick hatches.

The embryo needs food, water and oxygen to grow, so thin red blood vessels spread out from it over the yolk and then round the inside of the shell. The yolk provides most of the food, the albumen provides more protein and water and the oxygen passes through the shell and the membranes During the last few days the chick inside the egg begins to breathe with its lungs for the first time. To do this it needs an air supply inside the egg shell. At the big round end of the egg there is an air space. The chick makes a hole in this air space so that it can now breathe. The chick also peeps or calls to the hen through the shell. The hen then knows that the egg will soon hatch.

To escape from the egg the chick has a special point on its beak called an egg tooth. This egg tooth breaks holes in a circle all around the shell and the chick hatches. Here is a link to see actual pictures of this process.