The splanchnic mesoderm is a layer of mesodermal tissue that forms during early embryonic development. It is part of the three primary germ layers, which also include the ectoderm and endoderm. The splanchnic mesoderm contributes to the formation of various internal organs, including the heart, blood vessels, and parts of the digestive system. This layer is closely associated with the endoderm, which gives rise to the lining of the gastrointestinal tract and other internal organs. Together, the splanchnic mesoderm and endoderm play crucial roles in the development of the embryo and the formation of the visceral organs.