(redirected from Ectomesenchymal)
Also found in: Dictionary, Thesaurus, Medical.


That part of the mesoderm from which all connective tissues, blood vessels, blood, lymphatic system proper, and the heart are derived.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



the embryonic connective tissue in the majority of multicellular animals and man.

In the early stages of embryonic development, mesenchyme consists of motile dendriform cells. Most of these cells later lose their motility and unite by their processes into a network (syncytium) or form local aggregates. The mesenchyme originates from cells that have migrated from various germ layers. For example, the chief source of the mesenchyme in coelenterates, worms, and mollusks is the ectoderm (often also the endoderm), and in chordates and echinoderms, the mesoderm. Mesenchyme that originates from endoderm and mesoderm is called endomesenchyme, and mesenchyme originating from ectoderm (the material of the neural columns), ectomesenchyme. In vertebrates and man, endomesenchyme gives rise to various forms of connective tissue in the adult, formed elements of the blood, blood vessels, and smooth muscles. Almost the entire visceral skeleton (the auditory ossicles, gill arches), the pigment cells, and part of the derma are formed from ectomesenchyme.

The poorly differentiated connective-tissue cells (fibroblasts and reticular cells) found in animals and man during the postembryonic period are sometimes called mesenchyme.


Tokin, B. P. Obshchaia embriologiia, 2nd ed. Leningrad, 1970.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Gaillard et al., "The human nose harbors a niche of olfactory ectomesenchymal stem cells displaying neurogenic and osteogenic properties," Stem Cells and Development, vol.
Ameloblastic fibromas are a rare variety of benign odontogenic tumors composed of proliferating odontogenic epithelium embedded in a cellular ectomesenchymal tissue resembling dental papilla.
Ectomesenchymal signaling system between den- tal papilla and the internal enamel epithelium can affect tooth morphogenesis.24 These signals have specific roles such as tooth morphogenesis and the folding of enamel organ.25
These hypotheses included metaplastic cartilaginous transformation of pre-existing mesenchymal elements within the tumor, origin from multipotential neural crest--derived ectomesenchymal cells, or formation of cartilage directly by the multipotential neuroectodermal tumor cells.
However, these undifferentiated mesenchyme cells are originated from cranial neural crest cells, which are ectomesenchymal cells arising from the crests of the neural folds.
(1) The embryological derivation of these Schwann cells is during the fourth week of development from a specialized population of ectomesenchymal cells of the neural crest.
Yan et al., "Long-term expandable SOX9+ chondrogenic ectomesenchymal cells from human pluripotent stem cells," Stem Cell Reports, vol.
The proposes that each tooth is derived from a clone of ectomesenchymal cells programmed by the epithelium to produce a given pattern