embrüo

Embrüo is the early stage of development in a multicellular organism that begins after fertilization. It is the precursor to a fetus in animals and to a seedling in plants, and it encompasses the initial cellular divisions, differentiation, and patterning that establish the body plan. The term is used in biology and medicine to describe the pre-natal form before more recognizable features develop.

In animals, embrüo development typically proceeds through cleavage divisions that transform the fertilized egg into a multicellular structure such as a blastula, then into a gastrula that establishes the germ layers, and subsequently into organ primordia during organogenesis. In mammals, the embrüo is supported by extraembryonic membranes and later by the placenta as growth proceeds.

Human development: In humans, the embrüo period generally spans fertilization to about the end of the eighth to tenth week, after which development is described as the fetal period. It is during this time that essential tissues, organs, and body axes are established. Many embryos with severe chromosomal or structural abnormalities fail to continue developing.

Plant embrüo: In plants, the embrüo forms within the ovule and becomes part of the seed. The embryo contains a shoot and root axis and often cotyledons, which later emerge during germination to grow into a seedling. Plant embryogenesis includes characteristic stages such as globular and heart-shaped forms in many species.

Research and regulation: Embryo research includes studies on early development and the potential use of embryo-derived stem cells. In clinical contexts such as in vitro fertilization and embryo cryopreservation, ethical and legal questions arise. Many jurisdictions follow guidelines limiting embryo culture to about 14 days after fertilization, reflecting debates over moral status and potential.