Mesoderm

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Mesoderm
Image:Mesoderm.png
Organs derived from mesoderm.

Section through the embryo
Gray's	subject #6 49
MeSH	Mesoderm

The germ layer mesoderm forms in the embryos of animals more complex than cnidarians, making them triploblastic. Mesoderm forms during gastrulation when some of the cells migrating inward to form the endoderm form an additional layer between the endoderm and the ectoderm.

This key innovation evolved hundreds of millions of years ago and led to the evolution of nearly all large, complex animals. The formation of a mesoderm led to the formation of a coelom. Organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks.

1 Categorizing animals
2 Derivatives
- 2.1 General
- 2.2 Vertebrates
3 See also
4 Additional images
5 References
6 External links

[edit] Categorizing animals

Not all triploblastic animals have a coelom, like the simplest animals with organs that form from three tissue layers: flatworms. Three different configurations of mesoderm in relation to ectoderm form a method of categorizing animals.

Acoelomates
- no coelom
- tissues and organs packed between gut and body wall
Pseudocoelomates
- false coelom
- unlined or partially lined body cavity between gut and body wall
Coelomates
- proper coelom
- lined cavity between gut and body wall

[edit] Derivatives

[edit] General

Note: Not all triploblasts produce all of the items listed.

bones
most of the circulatory system, including the heart and major blood vessels
connective tissues of the gut and integuments
gastrointestinal tract
mesenchyme
mesothelium
muscles
peritoneum (lining of the coelom)
reproductive system
urinary system, including the kidneys

[edit] Vertebrates

Image:Image19.png

In addition to the general list, the mesoderm of a developing vertebrate differentiates into the following:

[edit] See also

[edit] Additional images

Section through ovum imbedded in the uterine decidua

Transverse section of a chorionic villus.

Primary chorionic villi. Diagrammatic.

Secondary chorionic villi. Diagrammatic.

[edit] References

Image:Wiktionary-logo-en.png

Look up mesoderm in
Wiktionary, the free dictionary.

Evers, Christine A., Lisa Starr. Biology:Concepts and Applications. 6th ed. United States:Thomson, 2006. ISBN 0-534-46224-3.

[edit] External links

Embryology at UNSW Notes/skmus6
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Embryology at Temple EMBIII97/sld039