The middle of the three primary germ layers of the embryo, lying between the ectoderm and entoderm; from it are derived the connective tissue, bone, cartilage, muscle, blood and blood vessels, lymphatics, lymphoid organs, notochord, pleura, pericardium, peritoneum, kidneys, and gonads.

  • somatic mesoderm the outer layer of the developing mesoderm.
  • splanchnic mesoderm the inner layer of the developing mesoderm.
Synonyms
Mesodermal, somatic mesoderm, splanchnic mesoderm