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Encyclopedia > Embryo
Embryos (and one tadpole) of the wrinkled frog (Rana rugosa)
Embryos (and one tadpole) of the wrinkled frog (Rana rugosa)

An embryo (from Greek: ἔμβρυον, plural ἔμβρυα, lit. "that which grows," from en- "in" + bryein "to swell, be full") 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 from the moment of fertilisation until the end of the 8th week, whereafter it is instead called a fetus. Look up embryo in Wiktionary, the free dictionary. ... Image File history File linksMetadata Wrinkledfrog_embryos. ... Image File history File linksMetadata Wrinkledfrog_embryos. ... For other uses, see Tadpole (disambiguation). ... Wild-type Caenorhabditis elegans hermaphrodite stained to highlight the nuclei of all cells Multicellular organisms are organisms consisting of more than one cell, and having differentiated cells that perform specialized functions. ... Ploidy is the number of homologous sets of chromosomes in a biological cell. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Look up Development in Wiktionary, the free dictionary. ... This does not adequately cite its references or sources. ... For other uses, see Birth (disambiguation). ... In most birds and reptiles, an egg (Latin ovum) is the zygote, resulting from fertilization of the ovum. ... Not to be confused with Gemination in phonetics. ... This article is about fertilisation in animals and plants. ... For other uses, see Fetus (disambiguation). ...



Main article: Embryogenesis

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 that has all the DNA of two parents. The resulting embryo derives 50 percent of its genetic makeup from each parent. 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. Embryogenesis is the process by which the embryo is formed and develops. ... Sexual reproduction is a union that results in increasing genetic diversity of the offspring. ... The term spermatid refers to the haploid male germ cell that results from secondary spermatocyte division. ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... For other meanings see Zygote (disambiguation). ... The structure of part of a DNA double helix Deoxyribonucleic acid, or DNA, is a nucleic acid molecule that contains the genetic instructions used in the development and functioning of all known living organisms. ... For other uses, see Plant (disambiguation). ... For other uses, see Animal (disambiguation). ... Typical phyla Chromalveolata Chromista Heterokontophyta Haptophyta Cryptophyta (cryptomonads) Alveolata Dinoflagellata Apicomplexa Ciliophora (ciliates) Cabozoa Excavata Euglenozoa Percolozoa Metamonada Rhizaria Radiolaria Foraminifera Cercozoa Archaeplastida (in part) Rhodophyta (red algae) Glaucophyta (basal archaeplastids) Amoebozoa Choanozoa Many others; classification varies Protists (IPA: (RP); (GenAm)), Greek protiston -a meaning the (most) first of all... Mitosis divides genetic information during cell division. ...

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. Blastulation. ... 1 - blastula, 2 - gastrula; orange - ectoderm, red - endoderm. ... Organogenesis is a stage of animal development where the ectoderm, endoderm, and mesoderm are formed. ... A blastocoel(e) or blastocele or cleavage cavity or segmentation cavity is the central region of a blastocyst. ... A blastomere is the structure which results from the divisions of a fertilised egg during embryonic development . ...

Human embryo at six weeks gestational age
Human embryo at six weeks gestational age[1]

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. However, the position and arrangement of the germ layers are highly species-specific, 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. It has been suggested that epiboly be merged into this article or section. ... Diploblasty is a condition of the ovum in which there are two primary germ layers: the ectoderm and endoderm. ... Triploblasty is a condition of the ovum in which there are three primary germ layers: the ectoderm, mesoderm, and endoderm. ... Organs derived from each germ layer. ... Endoderm is one of the germ layers formed during animal embryogenesis. ... The ectoderm is outermost of the three germ layers of the developing embryo, the other two being the mesoderm and the endoderm. ... The mesoderm is one of the three germ layers in the early developing embryo, the other two layers being the ectoderm and the endoderm. ... This article does not cite any references or sources. ... The neural crest, a component of the ectoderm, is one of several ridgelike clusters of cells found on either side of the neural tube in vertebrate embryos. ...

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.[citation needed] 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. In microbiology and cell and molecular biology, competence is the ability of a cell to take up extracellular (naked) DNA from its environment. ... Neurogenesis (birth of neurons) is the process by which neurons are created. ... For other uses, see Brain (disambiguation). ... The Spinal cord nested in the vertebral column. ... The Peripheral nervous system resides or extends outside the CNS central nervous system (the brain and spinal cord) to serve the limbs and organs. ... Angiogenesis is the physiological process involving the growth of new blood vessels from pre-existing vessels. ... Cartilage is a type of dense connective tissue. ... Myogenesis is the formation of muscular tissue, in particular during embryonic development. ... Osteogenesis imperfecta (OI), commonly known as brittle bone disease, is a group of genetic bone disorders. ...

Generally, if a structure pre-dates another structure in evolutionary terms, then it often appears earlier than the other in an embryo; this general observation is sometimes summarized by the phrase "ontogeny recapitulates phylogeny."[2] 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 rule is not absolute, but it is recognized as being partly applicable to development of the human embryo. The theory of recapitulation, also called the biogenetic law or ontogeny recapitulates phylogeny, is a theory in biology which attempts to explain apparent similarities between humans and other animals. ... For other uses, see Fish (disambiguation). ... Reptilia redirects here. ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria For the folk-rock band see The Mammals. ... The telencephalon (IPA: ) is the name for the forebrain, a large region within the brain to which many functions are attributed. ... A human brain. ...

Embryos of plants and animals

  • Plants: 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.
  • Animals: 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. In humans, the embryo is defined as the product of conception from implantation in the uterus 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.

Pinguicula grandiflora commonly known as a Butterwort Example of a cross section of a stem [1] Botany is the scientific study of plant life. ... The spermatophytes comprise those plants that produce seeds. ... A ripe red jalapeño cut open to show the seeds For other uses, see Seed (disambiguation). ... Hypocotyl is a botanical term for a part of a germinating seedling of a seed plant. ... In botany, the radicle is the first part of a seedling (a growing plant embryo) to emerge from the seed during germination. ... For the plant genus, see Cotyledon (genus). ... Not to be confused with Gemination in phonetics. ... The bryophytes are those embryophytes (land plants) that are non-vascular: they have tissues and enclosed reproductive systems, but they lack vascular tissue that circulates liquids. ... This article is about the group of pteridophyte plants. ... In plants that undergo alternation of generations, a gametophyte is the structure, or phase of life, that contains only half of the total complement of chromosomes: The sporophyte produces spores, in a process called meiosis. ... Eutheria is a classification system nearly synonymous with Placentalia. ... This does not adequately cite its references or sources. ... For other meanings see Zygote (disambiguation). ... A human ovum Sperm cells attempting to fertilize an ovum An ovum (plural ova) is a haploid female reproductive cell or gamete. ... For other uses, see Fetus (disambiguation). ... This article is about female reproductive anatomy. ... Parturition redirects here. ... Gestation is the carrying of an embryo or fetus inside a female viviparous animal. ...

The human embryo


A 10mm embryo from an ectopic pregnancy, still in the oviduct. This embryo is about five weeks old (or from the 7th week of pregnancy).
A 10mm embryo from an ectopic pregnancy, still in the oviduct. This embryo is about five weeks old (or from the 7th week of pregnancy).
See also: Human embryogenesis and Prenatal development

Week 1-3 5-7 days after fertilization, the blastula attaches to the wall of the uterus (endometrium). When it comes into contact with the endometrium it performs implantation. Implantation connections between the mother and the embryo will begin to form, including the umbilical cord. The embryo's growth centers around an axis, which will become the spine and spinal cord. The brain, spinal cord, heart, and gastrointestinal tract begin to form.[3] Image File history File links Download high-resolution version (1874x2000, 1514 KB) This image was selected as a Featured Picture on the English language Wikipedia on 29 November 2006. ... Image File history File links Download high-resolution version (1874x2000, 1514 KB) This image was selected as a Featured Picture on the English language Wikipedia on 29 November 2006. ... Human embryogenesis is the process of cell division and cellular differentiation of the human embryo during early prenatal development. ... This article is about prenatal development in humans. ... The endometrium is the inner membrane of the mammalian uterus. ... Implantation is a phenomenon in prenatal development, i. ... In placental mammals, the umbilical cord is a tube that connects a developing embryo or fetus to the placenta. ...

Week 4-5 Chemicals produced by the embryo stop the woman's menstrual cycle. Neurogenesis is underway, showing brain activity at about the 6th week.[citation needed] The heart will begin to beat around the same time. Limb buds appear where the arms and legs will grow later. Organogenesis begins. The head represents about one half of the embryo's axial length, and more than half of the embryo's mass. The brain develops into five areas, along with vertebra and bones beginning to form. The heart starts to beat and blood starts to flow.[3] Week 6-8 Myogenesis and neurogenesis have progressed to where the embryo is capable of motion, and the eyes begin to form. Organogenesis and growth continue. Hair has started to form along with all essential organs. Facial features are beginning to develop. At the end of the 8th week, the embryonic stage is over, and the fetal stage begins.[3] Menstrual cycle In the female reproductive system, the menstrual cycle is a recurring cycle of physiologic changes that occurs in reproductive age females of several mammals, including human beings and other apes. ... For other uses, see Mass (disambiguation). ... For other uses, see Fetus (disambiguation). ...


The status of the human embryo is debated by some bioethicists. Some Christian Ethicists believe that an embryo does, in fact, possess personhood. Gilbert Meileander, Christian ethics professor at the private Lutheran university Valparaiso University for example, identifies conception as the point at which a new individual human being comes into existence, since "when sperm and ovum join to form the zygote, the individual's genotype is established."[4] The NIH defines the embryonic stage as the beginning of developed human form [3] Bioethics is the ethics of biological science and medicine. ... For other uses, see Person (disambiguation). ... Valparaiso University, known colloquially as Valpo, is a private university located in the city of Valparaiso in the U.S. state of Indiana. ... NIH can refer to: National Institutes of Health Norwegian School of Sports Sciences: (Norges idrettshøgskole - NIH) Not Invented Here This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...


  1. ^ 3D Pregnancy (Image from gestational age of 6 weeks). Retrieved 2007-08-28. A rotatable 3D version of this photo is available here, and a drawing is available here.
  2. ^ Gould, Stephen. Ontogeny and Philogeny, page 206 (1977): "recapitulation was not 'disproved'; it could not be, for too many well-established cases fit its expectations."
  3. ^ a b c d NIH Medical Encyclopedia http://www.nlm.nih.gov/medlineplus/ency/article/002398.htm
  4. ^ Gilbert Meilander, Bioethics: A Primer for Christians (2nd ed.; Grand Rapids: Eerdmans, 2005), p. 29.

Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 240th day of the year (241st in leap years) in the Gregorian calendar. ...

See also

Preceded by
Stages of human development
Succeeded by

Embryogenesis is the process by which the embryo is formed and develops. ... This article or section is in need of attention from an expert on the subject. ... In vitro fertilization (IVF) is a technique in which egg cells are fertilized outside the mothers body in cases where conception is difficult or impossible through normal intercourse. ... Plant embryogenesis is a sexual or asexual reproductive process that forms new plants. ... Embryo space colonization is an interstellar space colonization proposal that involves sending a robotic mission to a terrestrial planet (having a biosphere) that transports frozen early-stage embryos. ... This article is about human pregnancy in biological females. ... Embryo adoption is the adoption of frozen human embryos created through in-vitro fertilization for subsequent frozen embryo transfer (FET) into the adoptive mothers uterus. ... Human sexuality is the expression of sexual feelings. ... For other meanings see Zygote (disambiguation). ... Human development is the process of growing to maturity and reaching ones full potential. ... For other uses, see Fetus (disambiguation). ...

External links

Wikimedia Commons has media related to:
The placenta (Latin for cake, referencing its appearance in humans) is an ephemeral organ present in placental vertebrates, such as eutherial mammals and sharks during gestation (pregnancy). ... Decidua is the term for the uterine lining (endometrium) during a pregnancy. ... Before the fertilized ovum reaches the uterus, the mucous membrane of the body of the uterus undergoes important changes and is then known as the decidua. ... Chorionic villi are villi that sprout from the chorion, in order to give a maximum area of contact with the maternal blood. ... The trophoblast proliferates rapidly and forms a network of branching processes which cover the entire ovum and invade and destroy the maternal tissues and open into the maternal bloodvessels, with the result that the spaces in the trophoblastic network are filled with maternal blood; these spaces communicate freely with one... The gestational sac is the only available intrauterine structure that can be used to determine if an intrauterine pregnancy (IUP) exists, until the embryo is identified. ... For the alien race in Stephen Donaldsons The Gap Cycle, see Amnion (Gap Cycle). ... A drawing of the amniotic sac from Grays Anatomy. ... amniotic sac The amniotic sac is a tough but thin transparent pair of membranes, which hold a developing embryo (and later fetus) until shortly before birth. ... For the entertainment company see Chorion (company) The chorion surrounds the embryo and other membranes. ... An Introduction to Histogenesis Histogenesis is defined as the formation of tissues and organs from undifferentiated cells (Encarta Dictionary). ... Programmed cell death (PCD) is the deliberate suicide of an unwanted cell in a multicellular organism. ... Mouse embryonic stem cells. ... The cells that give rise to the gametes are often set aside during cleavage. ... Organogenesis is a stage of animal development where the ectoderm, endoderm, and mesoderm are formed. ... The vertebrate limb arises out of a general morphogenetic area called a limb field. ... In embryology, the limb bud is a structure formed by the developing limb, derived from lateral plate mesoderm[citation needed]. It is intimately related with the apical ectodermal ridge, which secretes factors inducing the initial differentiation of the limb bud. ... The Apical Ectodermal Ridge (AER) is a critical component in vertebrate limb development. ... Transverse section showing the lens and the optic cup. ... Cutaneous structures arise from the epidermis and include a variety of features such as hair, feathers, claws and nails. ... The heart is the first functional organ in a vertebrate embryo. ... In prenatal development, the urinary and reproductive organs are developed from the intermediate mesoderm. ...

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