Mesoderm

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Introduction

The trilaminar embryo

The middle layer of the early trilaminar embryo germ layers (ectoderm, mesoderm and endoderm) formed by gastrulation.

This middle germ layer forms connective tissues and muscle throughout the body, with the exception of in the head region where some of these structures have a neural crest (ectoderm) origin.

  • connective tissues - cartilage, bone, blood, blood vessel endothelium, dermis, etc.
  • muscle - cardiac, skeletal, smooth.

Students often mix-up the terms mesoderm (middle layer) with mesenchyme (embryonic connective tissue). It is true that mesoderm initially does have a mesenchymal cellular organisation, but can also form a range of epithelial structures (surrounding somites, mesothelium lining of body cavities).


Mesoderm Links: Lecture - Mesoderm Development | Lecture - Musculoskeletal Development | Notochord | Development Animation - Notochord | Somitogenesis | Musculoskeletal | Sonic hedgehog | Category:Mesoderm

Some Recent Findings

  • Signaling gradients during paraxial mesoderm development[1] "These studies indicate that high levels of Wnt and FGF signaling are required for the segmentation clock activity. Furthermore, we discuss how these signaling gradients act in a dose-dependent manner in the progenitors of the paraxial mesoderm, partly by regulating cell movements during gastrulation. Finally, links between the process of axial specification of vertebral segments and Hox gene expression are discussed."
  • Transcriptional profiling of the nucleus pulposus: say yes to notochord[2]"This editorial addresses the debate concerning the origin of adult nucleus pulposus cells in the light of profiling studies by Minogue and colleagues. In their report of several marker genes that distinguish nucleus pulposus cells from other related cell types, the authors provide novel insights into the notochordal nature of the former. Together with recently published work, their work lends support to the view that all cells present within the nucleus pulposus are derived from the notochord. Hence, the choice of an animal model for disc research should be based on considerations other than the cell loss and replacement by non-notochordal cells."

Mesoderm Formation during Gastrulation

Chicken-gastrulation2.jpg

<mediaplayer width='390' height='500' image="http://php.med.unsw.edu.au/embryology/images/b/b9/Mesoderm_001_icon.jpg">File:Mesoderm_001.mp4</mediaplayer> This animation shows the migration of mesoderm throughout the embryonic disc during gastrulation.

The pink arrows show how mesodermal cells spread out between the ectoderm and endoderm layers, forming the third layer of the trilaminar embryo.

Axial process - the arrow running from the primitive node upward is the axial process which will later form the notochord.

There are only 2 regions where mesoderm is not found: buccopharyngeal membrane and cloacal membrane.

  • these two regions form the upper and lower ends of the gastrointestinal tract.

Prechordal plate - lies above the buccopharyngeal membrane and is the cardiogenic mesoderm, that will form the heart.

Links: Gastrulation

Patterning

Notochord secreting sonic hedgehog, shown in white
Neuralplate cartoon.png Somite cartoon5.png
Neural tube patterning Somite patterning

Molecular Factors

References

  1. <pubmed>20182616</pubmed>
  2. <pubmed>20497604</pubmed>

Reviews

<pubmed>20568241</pubmed>

<pubmed>17705304</pubmed>

Articles

<pubmed>21159819</pubmed> <pubmed>20565707</pubmed> <pubmed>7956820</pubmed>

Historic

<pubmed>17104422</pubmed>

Search PubMed

Search NLM Online Textbooks: "Mesoderm" : Developmental Biology | The Cell- A molecular Approach | Molecular Biology of the Cell | Endocrinology


Search Pubmed: Mesoderm | Notochord

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.

Take the Quiz

1

Mesenchyme refers to the middle layer of the trilaminar embryo

true
false

2

The intraembryonic coelom forms within :

somites
lateral plate
neural tube
intermediate mesoderm

3

All paraxial mesoderm segments into somites.

true
false

4

Somites are developmental structures that contribute the following adult structures :

vertebra, notochord, dermis, skeletal muscle
vertebra, intervertebral discs, dermis, skeletal muscle
kidney, body wall connective tissue, sensory ganglia
kidney, gastrointestinal tract smooth muscle, mesentry


Glossary Links

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Cite this page: Hill, M.A. (2019, September 21) Embryology Mesoderm. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Mesoderm

What Links Here?
© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G