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The formation of an embryo from a fertilized ovum, or zygote. Development begins when the zygote, originating from the fusion of male and female gametes, enters a period of cellular proliferation, or cleavage. Cells of the embryo subsequently give rise to the tissues and organs of the body in a temporal and spatial pattern that creates a functional, multicellular organism.

Following cleavage, the cells of the animal embryo rearrange into three germ layers: an outer ectoderm, a middle mesoderm, and an inner endoderm. Cells, responding to intrinsic and extrinsic factors, eventually segregate from the germ layers and organize into the rudiments of the tissues and organs of the body. These rudiments alter the size and the shape of the embryo, endowing the body with its axial symmetry. Cellular growth and differentiation are the principal processes that transform the rudiments into functional tissues and organs. Once the organs and organ systems are formed, further development consists primarily of growth. See Germ layers

Major features of embryogenesis in flowering plants include the formation of root and shoot apical meristems; differentiation of primary vascular tissue; the transition from a heterotrophic zygote to an embryo capable of independent growth and development; and preparations for desiccation, dormancy, and germination. See Apical meristem, Cell differentiation, Developmental biology, Embryology, Embryonic differentiation, Embryonic induction


The formation and development of an embryo from an egg.
References in periodicals archive ?
5 [micro]M of 2,4-D to obtain Vitis somatic embryogenesis [16, 17] for five consecutive years caused the accumulation of residues in the order of 70.
Embryogenesis and blastocyst development after somatic cell nuclear transfer in nonhuman primates: overcoming defects caused by meiotic spindle extraction.
demonstrated that somatic embryogenesis from zygotic embryo-derived
Following discoveries in the middle 1980s that immature embryos from Norway spruce seeds could be propagated or cloned in culture using somatic embryogenesis, we started a well-funded research and development program using this technology for both loblolly pine and Douglas-fir.
Thymic masses in the trachea and pharynx and at the base of the skull have also been reported[8] and likely result from an aberrant migration pathway in thymus embryogenesis.
The research center in Tours has been one of the world's first laboratories to have developed this technology of somatic embryogenesis.
This is an important datum because it shows that in the normal process of embryogenesis, the developing preimplantation embryo is not yet individualized.
When winter temperatures fell below 10[degrees] C, spermatogenesis ceased, thereby prohibiting fertilization and embryogenesis.
NORMAL AND ABNORMAL EMBRYOGENESIS OF THE MAMMALIAN BRAIN (Kathy Sulik, Shonagh O'Leary-Moore, Elizabeth Godin, and Scott Parnel, Chapel Hill, NC, USA).
We will also empirically evaluate global models of evolutionary conservation patterns during embryogenesis and placentation.
Dermal inclusion cysts are benign masses that arise as the result of the entrapment of ectodermal components during embryogenesis.
Among specific topics are why the choice of progestin matters in neuroprotection, neuroactive steroids and peripheral neuropathy, somatostatin and neuroprotection in the retina, thyroid hormone action on glioma cells, and the obligatory functions of gonadotropins and progestogens during early embryogenesis and their role in adults.