1.an animal organism in the early stages of growth and differentiation that in higher forms merge into fetal stages but in lower forms terminate in commencement of larval life
2.(botany) a minute rudimentary plant contained within a seed or an archegonium
1.(MeSH)The anatomical parts that make up an organism in the early stages of development.
EmbryoEm"bry*o (?), n.; pl. Embryos (#). [F. embryon, Gr. 'e`mbryon, perh. fr. � in (akin to L. � E. in) + � to be full of, swell with; perh. akin to E. brew.] (Biol.) The first rudiments of an organism, whether animal or plant; as: (a) The young of an animal in the womb, or more specifically, before its parts are developed and it becomes a fetus (see Fetus). (b) The germ of the plant, which is inclosed in the seed and which is developed by germination.
In embryo, in an incipient or undeveloped state; in conception, but not yet executed. “The company little suspected what a noble work I had then in embryo.” Swift.
EmbryoEm"bry*o, a. Pertaining to an embryo; rudimentary; undeveloped; as, an embryo bud.
Aborted Embryo • Chick Embryo • Delayed Embryo Implantation • Disintegration of Embryo • Embryo Cell Research • Embryo Creation, Research • Embryo Culture Techniques • Embryo Death • Embryo Development • Embryo Disintegration • Embryo Disposition • Embryo Experimentation • Embryo Implantation • Embryo Implantation Inhibition • Embryo Implantation Suppression • Embryo Implantation, Delayed • Embryo Loss • Embryo Organizers • Embryo Reduction • Embryo Research • Embryo Resorption • Embryo Transfer • Embryo and Fetal Development • Embryo, Chick • Embryo, Mammalian • Embryo, Non-Mammalian • Embryo, Nonmammalian • Embryo, Preimplantation • Human Embryo Research • Mammalian Embryo • Nonmammalian Embryo • Post-implantation Embryo Development • Postimplantation Embryo Development • Postnidation Embryo Development • Postnidation Embryo Development, Animal • Pre-implantation Embryo Development • Preimplantation Embryo Development • Prenidation Embryo Development, Animal • Research Embryo Creation • Tubal Embryo Stage Transfer • Tubal Embryo Transfer • embryo and foetus • tubal embryo transfer
Cleavage (embryo) • Embryo (1976 film) • Embryo (Dir en grey song) • Embryo (Pink Floyd song) • Embryo (band) • Embryo (disambiguation) • Embryo donation • Embryo drawing • Embryo space colonization • Embryo splitting • Embryo transfer • Embryo-carrying Interstellar Starship • Embryo-carrying interstellar spaceship • Embryo-carrying interstellar starship • List of World Embryo chapters • The Embryo Hunts in Secret • The Embryo's in Bloom • Trilaminar embryo • World Embryo
animal; animate being; beast; brute; creature; fauna[ClasseHyper.]
plant; flora; plant life; vegetable[ClasseHyper.]
science de classification (fr)[Classe]
Descripteurs EUROVOC (fr)[Thème]
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|Embryos (and one tadpole) of the wrinkled frog (Rana rugosa)|
An embryo (irregularly from Greek: ἔμβρυον, plural ἔμβρυα, lit. "that which grows," from en- "in" + bryein, "to swell, be full"; the proper Latinate form would be embryum) is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination. In humans, it is called an embryo until about eight weeks after fertilization (i.e. ten weeks Last Menstrual Period or LMP), and from then it is instead called a fetus.
The development of the embryo is called embryogenesis. In organisms that reproduce sexually, once a sperm fertilizes an egg cell, the result is a cell called the zygote, which possesses half the DNA of each of its two parents. In plants, animals, and some protists, the zygote will begin to divide by mitosis to produce a multicellular organism. The result of this process is an embryo.
In animals, the development of the zygote into an embryo proceeds through specific recognizable stages of blastula, gastrula, and organogenesis. The blastula stage typically features a fluid-filled cavity, the blastocoel, surrounded by a sphere or sheet of cells, also called blastomeres. The embryo of a placental mammal is defined as the organism between the first division of the zygote (a fertilized ovum) until it becomes a fetus. An ovum is fertilized in a fallopian tube through which it travels into the uterus. In humans, the embryo is defined as the product of conception after it is implanted in the uterus wall through the eighth week of development. An embryo is called a fetus at a more advanced stage of development and up until birth or hatching. In humans, this is from the eighth week of gestation. However, animals which develop in eggs outside the mother's body are usually referred to as embryos throughout development, e.g. one would refer to a chick embryo, not a "chick fetus" even at late stages.
During gastrulation the cells of the blastula undergo coordinated processes of cell division, invasion, and/or migration to form two (diploblastic) or three (triploblastic) tissue layers. In triploblastic organisms, the three germ layers are called endoderm, ectoderm, and mesoderm. The position and arrangement of the germ layers are highly species-specific, however, depending on the type of embryo produced. In vertebrates, a special population of embryonic cells called the neural crest has been proposed as a "fourth germ layer", and is thought to have been an important novelty in the evolution of head structures.
During organogenesis, molecular and cellular interactions between germ layers, combined with the cells' developmental potential, or competence to respond, prompt the further differentiation of organ-specific cell types. For example, in neurogenesis, a subpopulation of ectoderm cells is set aside to become the brain, spinal cord, and peripheral nerves. Modern developmental biology is extensively probing the molecular basis for every type of organogenesis, including angiogenesis (formation of new blood vessels from pre-existing ones), chondrogenesis (cartilage), myogenesis (muscle), osteogenesis (bone), and many others.
Generally, if a structure pre-dates another structure in evolutionary terms, then it often appears earlier than the second in an embryo; this general observation is sometimes summarized by the phrase "ontogeny recapitulates phylogeny". For example, the backbone is a common structure among all vertebrates such as fish, reptiles, and mammals, and the backbone also appears as one of the earliest structures laid out in all vertebrate embryos. The cerebrum in humans, which is the most sophisticated part of the brain, develops last. This sequencing rule is not absolute, but it is recognized as being partly applicable to development of the human embryo.
Fossilised animal embryos are known from the Precambrian, and are found in great numbers during the Cambrian period. Even fossilised dinosaur embryos have been discovered.
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Some embryos do not survive through to the fetal stage, which begins about two months after fertilization (10 weeks LMP). Embryos may be aborted spontaneously or purposely.
Studies using very sensitive early pregnancy tests have found that 25% of embryos are aborted by the sixth week LMP (since the woman's last menstrual period), even if a woman does not realize it. Abortions after the sixth week LMP happen in 8% of pregnancies. The risk of them is "virtually complete by the end of the embryonic period," with a rate of only two percent after 8.5 weeks LMP.
The most common natural cause of abortion of an embryo is chromosomal abnormality, which accounts for at least 50% of sampled early pregnancy losses. Advancing maternal age and a patient history of previous spontaneous abortions are the two leading risk factors.
The majority of induced abortions occur during the embryonic period. For example, in England and Wales during 2006, 68% of them occurred by the end of the embryonic period.
Induced (i.e. purposeful) abortion of an embryo may be accomplished by a variety of methods, including both pharmaceutical and surgical techniques. Suction-aspiration is the most common surgical method of aborting an embryo within the United States.
Common reasons for purposely aborting an embryo include a desire to delay or end childbearing, concern over the interruption of work or education, issues of financial or relationship stability, perceived immaturity and health concerns.
Embryos are used in various techniques of assisted reproductive technology, such as in vitro fertilization and embryo donation. They may be subject to embryo cryopreservation for later use if IVF procedures have resulted in more embryos than is currently needed. Some aspects, e.g. selective reduction, are issues in the beginning of pregnancy controversy.
Current medical technology does not allow an embryo to survive outside the uterus under any circumstances, or to be transplanted from the uterus of one woman to that of another. A human embryo is therefore not considered viable.
Human embryos are being researched to determine their use in treating diseases. Their use in stem cell research, reproductive cloning, and germline engineering are currently being explored. The morality of this type of research is debated because an embryo is often used.
Michael J. Fox, in the past one of the more famous proponents of embryonic stem cell research for its potential to help find a cure for Parkinson's Disease, recently withdrew his support for embryonic stem cell research, as opposed to adult stem cell research, citing the track record's lack of success which makes former hopes of embryonic stem cell research now appear over-estimated. There have not been any significant medical breakthroughs using embryonic stem cells. (http://nation.foxnews.com/michael-j-fox/2012/06/01/michael-j-fox-backs-embryonic-stem-cell-research) and (http://abcnews.go.com/blogs/health/2012/05/18/michael-j-fox-looks-past-stem-cells-in-search-for-parkinsons-cure/) and (http://thenewamerican.com/culture/item/11567-actor-michael-j-fox-back-off-optimism-over-embryonic-stem-cell-research)
In botany, a seed plant embryo is part of a seed, consisting of precursor tissues for the leaves, stem (see hypocotyl), and root (see radicle), as well as one or more cotyledons. Once the embryo begins to germinate — grow out from the seed — it is called a seedling. Plants that do not produce seeds, but do produce an embryo, include the bryophytes and ferns. In these plants, the embryo is a young plant that grows attached to a parental gametophyte.
|Stages of human development
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