Egg structures refer to the various components that make up an egg, primarily focusing on the shell, membranes, albumen, and yolk. The shell is the hard outer layer that protects the contents inside, while the membranes are thin layers just beneath the shell that provide additional protection and help prevent bacterial entry. Inside the egg, the albumen, or egg white, surrounds the yolk, which is the nutrient-rich part that supports the developing embryo in fertilized eggs. These structures work together to create a safe environment for growth and development, ensuring the embryo receives the necessary nutrients and protection.