Gastrulation: Difference between revisions
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== Human Gastrulation == | |||
The site of gastrulation, the primitive streak is visible during week 3 on the epiblast surface of the [[Carnegie stage 7|stage 7 embryonic disc]]. | |||
[[File:Stage7-sem4.jpg|400px|left]] | [[File:Stage7-sem4.jpg|400px|left]] | ||
[[File:Stage7-bf4.jpg|400px|left]] | [[File:Stage7-bf4.jpg|400px|left]] | ||
[[File:Stage7_primitive_streak_labelled.jpg]] | [[File:Stage7_primitive_streak_labelled.jpg]] | ||
== Gastrulation Concepts== | |||
[[File:Chicken-gastrulation2.jpg]] | [[File:Chicken-gastrulation2.jpg]] | ||
[[File:Chicken-gastrulation3.jpg]] | [[File:Chicken-gastrulation3.jpg]] |
Revision as of 08:18, 28 August 2009
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. 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.
Human Gastrulation
The site of gastrulation, the primitive streak is visible during week 3 on the epiblast surface of the stage 7 embryonic disc.
Gastrulation Concepts
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Cite this page: Hill, M.A. (2024, June 20) 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