Gastrulation produces three embryonic germ layers.

1. Ectoderm [outer layer] develops into epidermis of skin and the nervous system.
2. Mesoderm [middle layer] develops into skeletal, muscular, excretory, and the reproductive systems
3. Endoderm [inner layer] develops into epithelial lining of digestive and respiratory tracts + liver, pancreas and other associated glands.
   
   LMC Biology, 1999