organ part parenchyma EHDAA:3015 EHDAA:3905 EHDAA:3999 EHDAA:4005 EHDAA:6899 EHDAA:6903 EHDAA:6994 EHDAA:8086 EHDAA:9182 EHDAA:9190 EHDAA:9196 EHDAA:9202 Early in development the mammalian embryo has three distinct layers: ectoderm (external layer), endoderm (internal layer) and in between those two layers the middle layer or mesoderm. The parenchyma of most organs is of ectodermal (brain, skin) or endodermal origin (lungs, gastrointestinal tract, liver, pancreas). The parenchyma of a few organs (spleen, kidneys, heart) is of mesodermal origin. The stroma of all organs is of mesodermal origin FMA:45732 UBERON:0000353 UMLS:C0933845 functional part of an organ in the body. This is in contrast to the stroma, which refers to the structural tissue of organs, being exactly, connective tissues. parenchymal the FMA definition is more restrictive, and limits this to solid organs. This would seem to cause problems for the lung parenchyma, except FMA classifies Lung as solid rather than cavitated uberon