Mesenchyme

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Mesenchyme
MSC high magnification.jpg
Transmission electron micrograph of mesenchyme displaying the ultrastructure of a typical cell and matrix.
Mesenchyme.JPG
Mesenchyme (pointer) stained with H&E
Details
Carnegie stage 6b
Precursor primarily mesoderm
Identifiers
Latin mesenchyma
Code TE E5.16.4.0.3.0.18
Anatomical terminology

Mesenchyme is a type of tissue characterized by loosely associated cells that lack polarity and are surrounded by a large extracellular matrix.

Development[edit]

Mesenchymal cells are able to develop into the tissues of the lymphatic and circulatory systems, as well as connective tissues throughout the body, such as bone and cartilage. A sarcoma is a malignant cancer of mesenchymal cells.[1][2]

Morphology[edit]

Mesenchyme is characterized morphologically by a prominent ground substance matrix containing a loose aggregate of reticular fibrils and unspecialized cells.[3] Mesenchymal cells can migrate easily, in contrast to epithelial cells, which lack mobility and are organized into closely adherent sheets, and are polarized in an apical-basal orientation.

Invertebrate zoology[edit]

In some invertebrates - Porifera, Cnidaria, Ctenophora and some triploblasts (the acoelomates) - mesenchyme refers to a more-or-less solid but looselly organized tissue consisting of a gel matrix (the mesoglea) with various cellular and fibrous inclusions, located between epidermis and gastrodermis. In some cases, the mesoglea is noncellular.[4]

It is derived wholly or in part from ectoderm (not considered true mesoderm).[5]

In sponges, it is called mesohyl.[6]

In Cnidaria and Ctenophora, it is fully ectodermally derived. When cellular material is sparse or densely packed, the mesenchyme may be sometimes called collenchyme or parenchyme, respectively.[7]

When no cellular material is present (e.g., in Hydrozoa), the layer is properly called mesoglea.[8]

In some colonial cnidarians, the mesenchyme is perforated by gastrovascular channels continuous among colony members. This entire matrix of common basal material is called coenenchyme.[9]

In order to differentiate the use of the word mesenchyme in vertebrate embryology (that is, undifferentiated tissue found in embryonic true [ento-]mesoderm from which are derived all connective tissues, blood vessels, blood cells, the lymphatic system, and the heart) and the use in invertebrate zoology described above, some authors prefer to use the term mesoglea (in wider sense) in lieu of mesenchyme when referring to the middle layers of sponges and diploblasts, reserving the term mesenchyme for the embryological sense. However, Brusca & Brusca (2003) discourage this usage, using mesoglea in its strict sense, and preferring to maintain both the embryological and zoological senses for the term mesenchyme.[10]

Finally, some similar terms used in botany generally are differentiated by the suffix "a": mesenchyma (a tissue between xylem and phloem in roots), collenchyma (primordial leaf tissues) and parenchyma (supportive tissues).[11]

See also[edit]

References[edit]

  1. ^ Strum, Judy M.; Gartner, Leslie P.; Hiatt, James L. (2007). Cell biology and histology. Hagerstown, MD: Lippincott Williams & Wilkins. p. 83. ISBN 0-7817-8577-4. 
  2. ^ Sadler, T.W. (2006). Langman's Medical Embryology. Lippincott Williams & Wilkins. pp. 68–70. ISBN 0-7817-9485-4. 
  3. ^ Mesenchymal tissue
  4. ^ Brusca, R.C. & Brusca, G.J. (2003). Invertebrates. 2nd ed. Sunderland, Massachusetts: Sinauer Associates, p. 101.
  5. ^ Brusca & Brusca (2003), p. 220.
  6. ^ Brusca & Brusca (2003), p. 220.
  7. ^ Brusca & Brusca (2003), p. 220.
  8. ^ Brusca & Brusca (2003), p. 220.
  9. ^ Brusca & Brusca (2003), p. 220.
  10. ^ Brusca & Brusca (2003), p. 220.
  11. ^ Brusca & Brusca (2003), p. 220.

External links[edit]