Chickens lay eggs by pushing the ova through the reproductive tract. Along the way, the albumen, shell membranes, shell, and bloom are added, to feed and protect the ova inside. Once all of these parts have been added, the egg is laid.
- Activate eye glands
The receptors in hens' eyes are activated by specific light conditions. These conditions vary from breed to breed, but the light is a signal to the hen's body to release the ova and begin the egg-forming process.
- Send ova to infundibulum
The infundibulum is the place in a hen's body where sperm wait. If any are present for the 15 minutes the ova is there, the ova will be fertilized. After the ova leaves that area, it can no longer be fertilized.
- Send ova to magnum
The magnum is the place in the hen's body where the inner and outer shell membranes are added. The shell will be added at the very end, but these membranes are important to the egg's final formation
- Send ova to isthmus
The isthmus is where the albumen is secreted, layering itself around the ova. This process takes roughly an hour, and the albumen will serve as food for chicks in fertilized eggs.
- Send ova to uterus
In the uterus, water is added to the outer shell membrane, thinning it out. Then the shell material, which is primarily composed of calcium carbonate, forms around the albumen and ova combination. The shape of the hen's ovary dictates the shape of the shell, and the hen's diet dictates the coloration of the shell. Brown, white, blue and green eggs are the most common.
- Lay completed egg
This is the portion wherein the hen sits on her nest and pushes the egg from her body. It generally only takes one minute, and after laying, the hen leaves the nest. Leaving the nest allows the egg to cool, so that when the hen has enough eggs, she can sit on them and they will all hatch at once.