The endoderm is the innermost of the three germ layers, or masses of cells (lying within ectoderm and mesoderm), which appears early in the development of an embryo.
It will produce the gut and its associated organs, including the cecum, intestine, stomach, thymus, liver, pancreas, lungs, thyroid and prostate.
It will eventually come to form the lining of the digestive system in the human body, except for parts of the mouth, throat, and rectum.
The endoderm also gives rise to much of the internal epithelial tissue that lines organs and glands and also forms the airways in the lungs: the trachea, bronchi, and alveoli.
