germ layers

germ layers
The main divisions of tissue types in multicellular organisms. Diploblastic organisms (eg. coelenterates) have two layers, ectoderm and endoderm; triploblastic organisms (all higher animal groups) have mesoderm between these two layers. Germ layers become distinguishable during late blastula/early gastrula stages of embryogenesis, and each gives rise to a characteristic set of tissues, the ectoderm to external epithelia and to the nervous system for example, although some tissues contain elements derived from two layers.

Dictionary of molecular biology. 2004.

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Look at other dictionaries:

  • Derivatives of primary germ layers — ▪ Table Derivatives of primary germ layers Ectoderm epidermis cutaneous derivatives epithelium of:     mouth; oral glands     nasal passages     sense passages central nervous system peripheral nervous system hypophysis; suprarenal medulla… …   Universalium

  • germ layer — n any of the three primary layers of cells differentiated in most embryos during and immediately following gastrulation * * * any of the three distinct types of tissue found in the very early stages of embryonic development (see ectoderm,… …   Medical dictionary

  • primary germ layers — See: germ layer …   Glossary of Biotechnology

  • Germ layer — [ http://www.ncbi.nih.gov/About/primer/genetics cell.html NCBI] .] A germ layer is a collection of cells, formed during animal embryogenesis. Germ layers are particularly pronounced in the vertebrates; however, all animals more complex than… …   Wikipedia

  • germ layer theory — the theory that the embryo develops three primary germ layers, each of which gives rise to definite organ derivatives …   Medical dictionary

  • germ layer — any of the three distinct types of tissue found in the very early stages of embryonic development (see ectoderm, endoderm, mesoderm). The germ layers can be traced throughout embryonic development as they differentiate to form the entire range of …   The new mediacal dictionary

  • germ layer — germ′ lay er n. dvl any of the three primary embryonic cell layers Compare ectoderm,endoderm,mesoderm • Etymology: 1875–80 …   From formal English to slang

  • germ layer — n. Embryology any of the three primary layers of cells (ectoderm, endoderm, and mesoderm) from which the various organs and parts of the organism develop by further differentiation …   English World dictionary

  • germ layer — noun Date: 1877 any of the three primary layers of cells differentiated in most embryos during and immediately following gastrulation …   New Collegiate Dictionary

  • germ layer — see germinal layers …   Dictionary of invertebrate zoology

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