The endoderm is one of the three primary germ layers formed during embryonic development. It is the innermost layer and gives rise to various internal structures, including the lining of the digestive tract, respiratory system, and several glands. This layer plays a crucial role in forming organs such as the liver and pancreas. During the process of gastrulation, the endoderm is established alongside the mesoderm and ectoderm. Each of these layers contributes to the development of different tissues and organs in the body. The endoderm specifically focuses on creating the internal systems necessary for digestion and respiration.