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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.
This process makes a ball of embryonic cells which are capable of interacting, rather than a group of diffuse and undifferentiated cells. E-cadherin adhesion defines the apico-basal axis in the developing embryo and turns the embryo from an indistinct ball of cells to a more polarized phenotype which sets the stage for further development into ...
The filopodia—thin fibers formed by the mesenchyme cells, found in late gastrulation—contract to drag the tip of the archenteron across the blastocoel. The endoderm of the archenteron will fuse with the ectoderm of the blastocoel wall. At this point gastrulation is complete, and the embryo has a functional digestive tube.
In animals, the process involves a sperm fusing with an ovum, which eventually leads to the development of an embryo. Depending on the animal species, the process can occur within the body of the female in internal fertilization, or outside in the case of external fertilization. The fertilized egg cell is known as the zygote. [2] [5]
Another process, gastrulation of the embryo, is driven by Myosin II molecular motors, which are not conserved across species. The process may have been started by movements of sea water in the environment, later replaced by the evolution of tissue movements in the embryo. [56] [57]
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 ...
Through this process of mixing and continued digestion and absorption of nutrients, the chyme gradually works its way through the small intestine to the large intestine. [ 8 ] In contrast to peristalsis, segmentation contractions result in that churning and mixing without pushing materials further down the digestive tract.
Ingression is a very dynamic process however, and the first sign of an ingressing cell is seen when a future PMC loses its adhesion to hyaline, and cadherin, and increases its adhesion to a basal laminal substrate. These processes occur rapidly, over approximately 30 minutes. It is not understood how the PMCs penetrate the basal lamina.