Hens are born to lay eggs because they have genitals, just like women ovulate. But there are two kinds of eggs: one is fertilized and the other is unfertilized.

Fertilization is fertilization before the egg is born. After the cock and hen mate, the egg cells form fertilized eggs. The egg is fertilized in the oviduct funnel, then the oviduct expands to secrete albumin, and after ovulation, it enters the isthmus of oviduct for 2-3 hours. Granular cells secrete various components of eggshell membrane here, such as collagen X. At this time, the egg is wrapped in a membrane, which is the membrane that opens the eggshell when we eat eggs.

At this time, the fertilized egg has no eggshell. When the egg passes through the continuous section of fallopian tube, the eggshell is composed of multiple layers of mineral structures. Most of the calcium in eggshells is deposited in eggshells, and about 5-6g of calcium carbonate is deposited in eggshells.

At this time, an egg with a shell is formed, which will be laid by the hen. Under proper conditions, fertilized eggs can hatch into chickens.