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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

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.


The formation and development of an embryo from an egg.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Two hypothesizes for the potential mechanism of prostate tissue within rectal submucosa can be postulated from the normal embryologic origins of the prostate bladder and rectum which may be ex- plained on the basis of faulty embryogenesis. The rectum and bladder originate from the endodermal cloaca which is a single hollow tube.
Several studies have underlined the cultural techniques and the hormones needed to induce organogenesis or embryogenesis. Unfortunately, no data are available about comparative studies between the two techniques using the same hormones.
Somatic embryogenesis and plantlet regeneration from protoplast culture of Muscari neglectum Guss.
However, the selection of suitable types and sources of explant are critical factors for obtaining a successful culture in somatic embryogenesis system (FENG & CHEN, 2014).
The first studies on coconut somatic embryogenesis were performed in the 1980s using zygotic embryos, immature leaves and inflorescences as explants.
Although protocols for somatic embryogenesis have been reported in mahogany (Collado et al., 2006; Maruyama, 2009; Collado et al., 2010), to the best of our knowledge, no histological or biochemical analyses of SE development have been described.
The effect of different concentrations of growth regulators NAA and Kinetin on embryogenesis of chamomile (Matricaria chamomilla L.) explants:
Despite the advances observed in the study of somatic embryogenesis as reported by Reed et al.
Minerva Biotechnologies says it is the first company to generate human naive state induced pluripotent stem cells (iPS cells) using a single, naturally occurring human stem cell growth factor that is only expressed in the naive cells of the inner cell mass during the earliest days of embryogenesis.