Histogenesis
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2008-04-09T12:39:25Z
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robot Adding: [[cs:Histogeneze]]
[[Image:Endoderm_Mesoderm_Ectoderm.png|thumb|500px|This [[depiction]] represents the [[endoderm]], [[mesoderm]], and [[ectoderm]] respectively.]]
'''Histogenesis''' is the formation of different [[Biological tissue|tissues]] from undifferentiated [[cell (biology)|cells]].[http://www.encarta.msn.com/dictionary_/Histogenesis.html] These cells are constituents of three primary [[germ layer]]s, the [[endoderm]], [[mesoderm]], and [[ectoderm]]. The science of the microscopic structures of the tissues formed within histogenesis is termed [[histology]].
==Germ layers==
[[Image:Gastrulation.png|thumb|300px|'''[[Gastrulation]] of a [[diploblasty|diploblast]]:''' The formation of germ layers from a (1) [[blastula]] to a (2) [[gastrula]]. Some of the ectoderm cells (orange) move inward forming the endoderm (red).]]
{{main|Germ layer}}
A '''germ layer''' is a collection of [[cell (biology)|cell]]s, formed during animal and mammalian [[embryogenesis]]. Germ layers are typically pronounced within [[vertebrate]] organisms; however,[[animal]]s or mammals more complex than [[sea sponge|sponge]]s ([[eumetazoa]]ns and [[wikispecies:agnotozoa|agnotozoans]]) produce two or three primary tissue layers. Animals with [[symmetry (biology)#Radial symmetry|radial symmetry]], such as [[cnidaria]]ns, produce two layers, called the [[ectoderm]] and [[endoderm]]. Therefore, they are [[diploblastic]]. Animals with [[symmetry (biology)#Bilateral symmetry|bilateral symmetry]] produce a third layer in-between called [[mesoderm]], making them [[triploblastic]]. Germ layers will eventually give rise to all of an animal’s or mammal's [[biological tissue|tissues]] and [[organ (anatomy)|organ]]s through a process called [[organogenesis]].
===Endoderm===
{{main|Endoderm}}
The '''endoderm''' is one of the germ layers formed during animal embryogenesis. Cells migrating inward along the [[archenteron]] form the inner layer of the [[gastrula]], which develops into the [[endoderm]]. Initially, the endoderm consists of flattened cells, which subsequently become columnar.
===Mesoderm===
{{main|Mesoderm}}
The '''mesoderm''' germ layer forms in the [[embryo]]s of [[animal]]s and [[mammal]]s more complex than [[cnidaria]]ns, making them [[triploblastic]]. During [[gastrulation]], 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 [[body cavity|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.
===Ectoderm===
{{main|Ectoderm}}
The '''ectoderm''' is the start of a tissue that covers the body surfaces. It emerges first and forms from the outermost of the [[germ layer]]s.
==Production==
[[Image:Germ_layers.png|thumb|575px|The [[endoderm]] produces tissue within the [[lung]]s, [[thyroid]], and [[pancreas]]. The [[mesoderm]] aids in the production of [[cardiac muscle]], [[skeletal muscle]], [[smooth muscle]], tissues within the [[kidney]]s, and [[red blood cell]]s. The [[ectoderm]] produces tissues within the [[Epidermis (skin)|epidermis]] and aids in the formation of [[neuron]]s within the brain, and [[melanocytes]].]]
[[Image:cell differentiation.gif|right|thumb|300px|Organs derived from each germ layer. Image from [http://www.ncbi.nih.gov/About/primer/genetics_cell.html NCBI].]]
The proceeding graph represents the products produced by the three germ layers.
{| class="wikitable"
! Germ Layer !! Category !! Product
|-
| Endoderm || General<ref>The '''General''' category denotes that all or most of the [[animal]]s containing this layer produce the adjacent product.</ref> || [[Gastrointestinal tract]]
|-
| Endodern || General || [[Respiratory tract]]
|-
| Endoderm || General || [[Endocrine]] glands and organs ([[liver]] and [[pancreas]])
|-
| Mesoderm || General || [[skeletal system|Bones]]
|-
| Mesoderm || General || Most of the [[Circulatory system]]
|-
| Mesoderm || General || [[Connective tissue]]s of the gut and [[integumentary system|integuments]]
|-
| Mesoderm || General || [[gastrointestinal tract#Lower gastrointestinal tract|Excretory Tract]]
|-
| Mesoderm || General || [[Mesenchyme]]
|-
| Mesoderm || General || [[Mesothelium]]
|-
| Mesoderm || General || [[Muscular system|Muscles]]
|-
| Mesoderm || Gemeral || [[Peritoneum]]
|-
| Mesoderm || General || [[Reproductive System]]
|-
| Mesoderm || General || [[Urinary System]]
|-
| Mesoderm || Vertebrate<ref>The '''Vertebrate''' category denotes that all or most of the [[vertebrate]]s containing this layer produce the adjacent product.</ref> || [[Chordamesoderm]]
|-
| Mesoderm || Vertebrate || [[Paraxial mesoderm]]
|-
| Mesoderm || Vertebrate || [[Intermediate mesoderm]]
|-
| Mesoderm || Vertebrate || [[Lateral plate mesoderm]]
|-
| Ectoderm || General || [[Nervous system]]
|-
| Ectoderm || General || Outer part of [[integumentary system|integument]]
|-
| Ectoderm || Vertebrate || [[Skin]] (along with [[glands]], [[hair]], [[nail (anatomy)|nails]])
|-
| Ectoderm || Vertebrate || [[Epithelium]] of the [[mouth]] and [[nasal cavity]]
|-
| Ectoderm || Vertebrate || [[lens (vision)|Lens]] and [[cornea]] of the [[eye]]
|-
| Ectoderm || Vertebrate || [[Melanocytes]]
|-
| Ectoderm || Vertebrate || [[Peripheral nervous system]]
|-
| Ectoderm || Vertebrate || Facial [[cartilage]]
|-
| Ectoderm || Vertebrate || [[Dentin]] (in teeth)
|-
| Ectoderm || Vertebrate || [[Brain]] ([[rhombencephalon]], [[mesencephalon]] and [[prosencephalon]])
|-
| Ectoderm || Vertebrate || [[Spinal cord]] and [[motor neuron]]s
|-
| Ectoderm || Vertebrate || [[Retina]]
|-
| Ectoderm || Vertebrate || [[Posterior pituitary]]
|}
==See also==
*[[Histology]]
==References==
<div class="references-small">
<references />
* Microsoft Corporation. [http://www.encarta.msn.com/dictionary_/Histogenesis.html Histogenesis]. ''Encarta World English Dictionary (North American Edition)''. URL accessed on [[14 May]] [[2005]].
* Evers, Christine A., Lisa Starr. ''Biology:Concepts and Applications.'' 6th ed. United States:Thomson, 2006. ISBN 0-534-46224-3.
</div>
==External links==
{{wiktionary|histogenesis}}
*{{en icon}} [http://www.uoguelph.ca/zoology/devobio/splab7/index.htm Derivatives of the Ectoderm]
*{{en icon}} [http://www.uoguelph.ca/zoology/devobio/splab8/index.htm Derivatives of the Endoderm and Mesoderm]
{{Embryology}}
{{Germ layer}}
[[Category:Developmental biology]]
[[Category:Embryology]]
[[Category:Histology]]
[[cs:Histogeneze]]
[[fr:Histogenèse]]
[[pl:Histogeneza]]
[[pt:Histogênese]]
[[ru:Гистогенез]]
[[sr:Хистогенеза]]
[[uk:Гістогенез]]