ekstraembryonalt

Ekstraembryonalt (extraembryonal) describes components located outside the embryo proper but essential to its development. The term is used in embryology, anatomy, and pathology to differentiate structures that are part of the conceptus but are not part of the embryo itself.

Key examples are the extraembryonic membranes: amnion, chorion, and yolk sac, as well as the allantois in some species. In mammals, the placenta is formed largely from extraembryonic tissues and functions to facilitate nutrient transfer and gas exchange between mother and fetus. These structures provide protection, nutrition, waste management, and, in birds and reptiles, the yolk sac also supports early embryonic needs.

Terminology: ekstraembryonalt is used to indicate tissue located outside the embryo and/or of extraembryonic lineage. It is often contrasted with intraembryonal or embryonic tissues. The term is common in descriptive embryology and comparative anatomy.