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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. [2]
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 ...
Organogenesis is the phase of embryonic development that starts at the end of gastrulation and continues until birth. During organogenesis, the three germ layers formed from gastrulation (the ectoderm, endoderm, and mesoderm) form the internal organs of the organism. [1] The endoderm of vertebrates produces tissue within the lungs, thyroid, and ...
During this stage, the zygote divides in a process called cleavage. A blastocyst is then formed and implants in the uterus. Embryogenesis continues with the next stage of gastrulation, when the three germ layers of the embryo form in a process called histogenesis, and the processes of neurulation and organogenesis follow.
Drosophila embryogenesis, the process by which Drosophila (fruit fly) embryos form, is a favorite model system for genetics and developmental biology. The study of its embryogenesis unlocked the century-long puzzle of how development was controlled, creating the field of evolutionary developmental biology . [ 1 ]
The ectoderm can first be observed in amphibians and fish during the later stages of gastrulation. At the start of this process, the developing embryo has divided into many cells, forming a hollow ball called the blastula. The blastula is polar, and its two halves are called the animal hemisphere and vegetal hemisphere. It is the animal ...
The coelom is the mesodermally lined cavity between the gut and the outer body wall. During the development of the embryo, coelom formation begins in the gastrulation stage. The developing digestive tube of an embryo forms as a blind pouch called the archenteron. In protostomes, the coelom forms by a process known as schizocoely. [6]
Reptile gastrulation differs slightly from birds and mammals. Reptiles exhibit bi-modal gastrulation during embryogenesis and lack a primitive streak. Bi-modal gastrulation is characterized by involution of the cells in the anterior and lateral regions of the blastopore and ingression of the cells of the blastopore plate in the posterior region ...