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The archenteron, also called the gastrocoel, the primitive digestive tube or the primitive gut, is the internal cavity of the primitive gastrointestinal tract that forms during gastrulation in a developing animal embryo. It develops into the endoderm and mesoderm of the animal.
The blastula develops into a structure called a gastrula through a process called gastrulation. The gastrula then undergoes further development, including the formation of organs ( organogenesis ). The embryo then transforms into the next stage of development, the nature of which varies among different animal species (examples of possible next ...
Epiboly in zebrafish is the first coordinated cell movement, beginning at the dome stage late in the blastula period and continuing throughout gastrulation. [3] At this point the zebrafish embryo contains three portions: an epithelial monolayer known as the enveloping layer (EVL), a yolk syncytial layer (YSL) which is a membrane-enclosed group of nuclei that lie on top of the yolk cell, and ...
Before gastrulation, the embryo is a continuous epithelial sheet of cells; by the end of gastrulation, the embryo has begun differentiation to establish distinct cell lineages, set up the basic axes of the body (e.g. dorsal–ventral, anterior–posterior), and internalized one or more cell types including the prospective gut.
In birds, the organizer is known as Hensen's node, named after its discoverer Victor Hensen. In other amniotes, it is known as the primitive node. In amphibians, it is known as the Spemann-Mangold organizer, named after Hans Spemann and Hilde Mangold, who first identified the organizer in 1924. [1]) In fish, it is known as the embryonic shield. [2]
An alternative way to develop two openings from the blastopore during gastrulation, called amphistomy, appears to exist in some animals, such as nematodes. [3] [4] In humans, the perforation of the mouth and anus happen at four weeks and eight weeks respectively. [5]
[28] [29] However, in chickens and mice, bending at this hinge point is mediated by a process called basal wedging, rather than apical constriction. [12] [30] [31] In this case, the cells are so thin that the movement of the nucleus to the basal side of the cell causes a bulge in the basal part of the cell. This process may be regulated by how ...
During the third week, a process called gastrulation creates a mesodermal layer between the endoderm and the ectoderm. This process begins with the formation of a primitive streak on the surface of the epiblast. [6] The cells of the layers move between the epiblast and the hypoblast, and begin to spread laterally and cranially.