1. Vitelline Membrane:
The vitelline membrane is a thin, transparent layer that directly surrounds the embryo. It is semipermeable, allowing essential substances to enter while preventing harmful substances from reaching the embryo.
2. Albumen (Egg White):
The albumen is the thick, viscous fluid that makes up a large portion of the egg. It contains various proteins, such as albumins and globulins, which provide nutrition to the embryo. It also serves as a physical barrier, protecting the embryo from mechanical stress.
3. Chalazae:
Chalazae are ropey, twisted strands of albumen that anchor the yolk in the center of the egg. They prevent the yolk from coming in direct contact with the shell, reducing the risk of damage to the embryo.
4. Yolk Sac:
The yolk sac is a sac-like structure attached to the embryo. It contains a rich supply of yolk, which serves as a source of nutrients for the embryo's growth and development. The yolk is composed of lipids, proteins, and other essential nutrients.
5. Eggshell:
The eggshell is a protective, rigid outer covering that encloses the entire egg. It is made of calcium carbonate and other minerals, providing structural support and preventing the entry of harmful microorganisms or substances from the external environment.
6. Air Cell:
The air cell is a small pocket of air located at the blunt end of the egg. It helps in the embryo's respiration by allowing the exchange of oxygen and carbon dioxide. As the embryo develops, it consumes oxygen and produces carbon dioxide, which accumulate in the air cell.
These layers work synergistically to create a protective environment for the developing embryo, providing essential nutrients, physical support, and protection against external factors. They ensure that the embryo can undergo proper development until it is ready to hatch.