Gastrulation
Embryology - 19 Jun 2024 Expand to Translate |
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Introduction
Gastrulation means the formation of gut (Greek, gastrula = belly), but has now a more broad sense to to describe the formation of the trilaminar embryo. The epiblast layer, consisting of totipotential cells, derives all 3 embryo layers: endoderm, mesoderm and ectoderm. The primitive streak is the visible feature which represents the site of cell migration to form the additional layers.
Historically, gastrulation was one of the earliest observable morphological event occurring in the frog embryo. Currently, the molecular and physical mechanisms that regulate patterning and migration during this key event are being investigated in several different animal models. This region was also called the "Spemann's organiser" after Hans Spemann (1869 - 1941) who identified the region in amphibia. The same region in birds it is known as "Hensen's node" named for Victor Hensen (1835 – 1924) and is also known generally as the primitive node or knot. In humans, it is proposed that similar mechanisms regulate gastrulation to those found in other vertebrates.
- primitive node - region in the middle of the early embryonic disc epiblast from which the primitive streak extends caudally (tail)
- nodal cilia establish the embryo left/right axis
- axial process extends from the nodal epiblast
- primitive streak - region of cell migration from the epiblast layer forming sequentially the two germ cell layers (endoderm and mesoderm)
Epithelial to Mesenchymal Transition
Epithelial cells (organised cellular layer) which loose their organisation and migrate/proliferate as a mesenchymal cells (disorganised cellular layers) are said to have undergone an Epithelial Mesenchymal Transition (EMT). Mesenchymal cells have an embryonic connective tissue-like cellular arrangement, that have undergone this process may at a later time and under specific signaling conditions undergo the opposite process, mesenchyme to epithelia. In development, this process can be repeated several times during tissue differentiation.
This process occurs at the primitive streak where epiblast cells undergo an epithelial to mesenchymal transition in order to delaminate and migrate.
Links: gastrulation | Lecture - Week 3 | Week 3 | Carnegie stage 7 | Carnegie 8 | endoderm | mesoderm | ectoderm | Epithelial Mesenchymal Transition | notochord | ||
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Some Recent Findings
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More recent papers |
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This table allows an automated computer search of the external PubMed database using the listed "Search term" text link.
More? References | Discussion Page | Journal Searches | 2019 References | 2020 References Search term: Gastrulation <pubmed limit=5>Gastrulation</pubmed> |
Gastrulation Movies
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mesoderm spread | mouse cilia | quail extracellular matrix | Planar cell movement | Mesoderm migration |
Human Gastrulation
The site of gastrulation, the primitive streak is visible during week 3 on the epiblast dorsal surface of the embryonic disc.
Stage 7
- Links: Carnegie stage 7
Stage 8
Primitive pit |
Primitive groove and primitive streak |
- Links: Carnegie stage 8
Gastrulation Concepts
- Links: Chicken Development
Germ Layer Markers
Stem cell researchers have used the following markers to identify early differentiation of cells in the three germ layer in embryoid bodies.[6]
- Ectoderm - SOX1
- Mesoderm - Brachyury T
- Endoderm - Alpha-Fetoprotein
- Links: Induced Stem Cells | Alpha-Fetoprotein
Frog Gastrulation
Frog Gastrulation[7]
(A) The blastula stage, prior to any gastrulation movement. (B) Movement of the blastula cells preliminary to gastrulation. (C) Blastoporal view of successive phases of gastrulation; (solid line) lip of blastopore, {dotted line) germ ring, to be subsequently incorporated into the blastoporal lips. (D) Lateral view of sagittal section during late gastrulation showing the origin of the mesial notochord, and the lateral mesoderm from the proliferated chorda-mesoderm cells at the dorsal lip. (E) Composite drawing to illustrate the germ layer relations in the later gastrula of the frog. The medullary plate (ectoderm) is not indicated; {alternate dots and dashes) notochord, {heavy stippling) notochord, {sparse stippling) mesoderm, (cellular markings) ectoderm. |
- Links: Frog Development
Zebrafish Gastrulation
Kupffer's vesicle (ciliated organ of asymmetry, primitive node) a transient epithelial fluid-filled sac located midventrally posterior to the yolk cell or its extension. The vesicle has been described as equivalent to the primitive node for establishing embryo left-right (L-R) axis.[8]
- Links: Zebrafish Development
Additional Images
References
Reviews
<pubmed></pubmed> <pubmed></pubmed> <pubmed>26667903</pubmed> <pubmed>20566281</pubmed> <pubmed>20298258</pubmed> <pubmed>19945376</pubmed> <pubmed>19761865</pubmed> <pubmed>19253398</pubmed> <pubmed>18721878</pubmed> <pubmed>16344860</pubmed> <pubmed>11170350</pubmed> <pubmed>10369659</pubmed>
Articles
<pubmed></pubmed> <pubmed></pubmed> <pubmed>23204916</pubmed> <pubmed>21761476</pubmed> <pubmed>20485500</pubmed>
Books
Search Pubmed
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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.
- Gastrulation: From Cells to Embryo Supplemental Data and Figures
Glossary Links
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Cite this page: Hill, M.A. (2024, June 19) Embryology Gastrulation. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Gastrulation
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G