Mesenchyme

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mesenchyme

[′mez·ən‚kīm]
(embryology)
That part of the mesoderm from which all connective tissues, blood vessels, blood, lymphatic system proper, and the heart are derived.

Mesenchyme

 

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.

REFERENCE

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

T. A. DETLAF

References in periodicals archive ?
The parotid gland is formed by the proliferating ectoderm of the primitive oral cavity, which invaginates into the adjacent mesenchyma during the sixth week of pre-natal development.
The scarcity of smooth muscle in the head and neck compels one to consider that an aberrant differentiation of mesenchyma might be a causative factor.
Several theories have been proposed to explain the development of ectopic liver at different sites: development of an accessory lobe of the liver with atrophy or regression of the original connection to the main liver, (4) migration or displacement of a portion of the cranial part (Pars hepatica) of the liver bud to other sites, (6) dorsal budding of hepatic tissue before the closing of the pleuroperitoneal canal (may explain how EL develops in the thoracic cavity such as esophagus, pericardium, intra pleural or extra pleural), (7) trapping of hepatocyte-destined mesenchyma in different areas (8) and entrapment of nests of cells in the region of the foregut following closure of the diaphragm or umbilical ring.