title: Developmental stages of human embryos.
abstract: The embryonic period of human development was divided into eight main stages described as 1--unicellular, 2--blastomere stage, 3--blastoderm stage, 4--bilaminar stage, 5--trilaminar stage, 6--early somite stage, 7--stage of limb development, 8--late embryonic stage. These main groups were divided into further sub-groups. For description the decimal classification was used. The recommended classification is suitable for comparative purposes and was compared with hitherto used classifications of human embryos, in particular with Streeter's horizons.
mesh_terms: D001755:Blastocyst; D002454:Cell Differentiation; D002965:Classification; D004622:Embryo, Mammalian; D005855:Germ Layers; D005865:Gestational Age; D006128:Growth; D006801:Humans