Incubation and Embryology - University of Illinois

Take a Look Inside — How a Hen Lays an Egg

Inside the hen many things occur before an egg is laid. Let's see what happens in her body to make an egg. Inside the hen there is an ovary and an oviduct. The ovary is an organ which looks like a cluster of grapes. These clusters are follicles. Follicles are called egg yolks once the egg is laid by the hen. They are stored in the ovary until one day when they begin to grow. The follicles ovulate or burst from the ovary. Once ovulated, the follicle travels down a long tube called the oviduct.

The egg makes its journey to the outside world by moving through the oviduct. In the oviduct, the albumen or egg white is made. The albumen is formed over the follicle or egg yolk. That is why the yolk is always in the center of the egg. Also, two shell membranes and the shell are formed. When the hen lays an egg, the egg passes out the end of the oviduct. It leaves the hen's body. It takes from 24 to 26 hours for the egg to be laid. Even a good hen cannot lay more that one egg a day.

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