An embryo (from Greek: ἔμβρυον, plural ἔμβρυα, lit. A tadpole or polliwog (also pollywog, polliwig, polewig, or polwig) is the wholly aquatic larval stage in the life cycle of Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly "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. Multicellular organisms are Organisms consisting of more than one cell, and having Differentiated cells that perform specialized functions "Haplo" redirects here For the fictional character see The Death Gate Cycle. Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells. Birth is the act or process of bearing or bringing forth Offspring. In most Birds and Reptiles an egg ( Latin ovum) is the Zygote, resulting from Fertilization of the Ovum. Germination is the process whereby growth emerges from a period of dormancy 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. For soil improvement see Fertilization (soil. A fetus (or foetus or fœtus) is a developing Mammal or other Viviparous Vertebrate, after the Embryonic stage and
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Development
The development of the embryo is called embryogenesis. Embryogenesis is the process by which the Embryo is formed and develops 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 Evolution of sexual reproduction is a major puzzle The first Fossilized evidence of sexually reproducing Organisms is from Eukaryotes of the Stenian The term spermatid refers to the Haploid male Gametid that results from division of secondary Spermatocytes As a result of Meiosis, each spermatid An ovum (plural ova) is a Haploid Female reproductive cell or Gamete. The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known 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. Plants are living Organisms belonging to the kingdom Plantae. Protists (ˈproʊtɨst are a diverse group of eukaryotic Microorganisms Historically protists were treated as the kingdom Protista but this Mitosis is the process in which a Eukaryotic cell separates the Chromosomes in its Cell nucleus, into two identical sets in two daughter nuclei The result of this process is an embryo.
In animals
In animals, the development of the zygote into an embryo proceeds through specific recognizable stages of blastula, gastrula, and organogenesis. The blastula is an early stage of Embryonic development in Animals It is also called blastosphere Gastrulation is a phase early in the development of animal Embryos during which the morphology of the embryo is dramatically restructured by Cell migration. In animal development, organogenesis is the process by which the Ectoderm, Endoderm, and Mesoderm develop into the Internal organs The blastula stage typically features a fluid-filled cavity, the blastocoel, surrounded by a sphere or sheet of cells, also called blastomeres. A blastocoel(e or blastocele (also called blastocyst cavity, cleavage cavity or segmentation cavity) is the Fluid -filled central A blastomere is a type of cell produced by division of the egg after fertilization.
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. Gastrulation is a phase early in the development of animal Embryos during which the morphology of the embryo is dramatically restructured by Cell migration. 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 Blastula in which there are three primary Germ layers the Ectoderm, Mesoderm, and Endoderm. In triploblastic organisms, the three germ layers are called endoderm, ectoderm and mesoderm. A germ layer is a collection of cells formed during animal Embryogenesis. Endoderm, (sometimes called Entoderm) is one of the Germ layers formed during animal Embryogenesis. The ectoderm is the start of a tissue that covers the body surfaces One of the three Germ layers found in the Embryos of Animals more complex than Cnidarians making them Triploblastic. 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. Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes The neural crest, a transient component of the Ectoderm, is located in between the Neural tube and the epidermis (or the free margins of the Neural folds
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. In Microbiology, Genetics, Cell biology and Molecular biology, competence is the ability of a cell to take up extracellular ("naked" For example, in neurogenesis, a subpopulation of ectoderm cells is set aside to become the brain, spinal cord and peripheral nerves. Neurogenesis ( birth of Neurons ' is the process by which neurons are created The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain The spinal cord is a long thin tubular bundle of Nerves that is an extension of the Central nervous system from the brain and is enclosed in and protected The peripheral nervous system ( PNS) resides or extends outside the Central nervous system (CNS which consists of the Brain and Spinal cord. 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. Angiogenesis is a physiological process involving the growth of new Blood vessels from pre-existing vessels Cartilage is a type of dense Connective tissue. It is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix Myogenesis is the formation of muscular tissue in particular during embryonic development Osteogenesis is the process of laying down new Bone material by Osteoblasts It occurs in two different ways Either by Intramembranous Osteogenesis (see Intramembranous
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. The theory of recapitulation, also called the biogenetic law or embryological parallelism, and often expressed as Ontogeny recapitulates Phylogeny "[1] 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. Fish are aquatic Vertebrate animals that are typically ectothermic (previously Cold-blooded) covered with scales, and equipped with two Reptiles, or members of the class Reptilia are air-breathing Cold-blooded Vertebrates that have skin covered in scales as opposed to hair or feathers Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands The cerebrum in humans, which is the most sophisticated part of the brain, develops last. The telencephalon (tɛlɛnˈsɛfəlɒn cerebrum, or forebrain is the most Anterior or especially in humans most Dorsal region of the The human brain controls the Central nervous system (CNS by way of the Cranial nerves and Spinal cord, the Peripheral nervous system (PNS This rule is not absolute, but it is recognized as being partly applicable to development of the human embryo.
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. Botany, plant science(s, phytology, or plant biology is a branch of Biology and is the scientific study of plant Life The spermatophytes (from the Greek word "Σπερματόφυτα" (also known as phanerogams) comprise those Plants that produce Seeds They are A seed (in some plants referred to as a kernel) is a small embryonic Plant enclosed in a covering called the seed coat usually with some stored 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 the process of A cotyledon ("seed leaf" from Greek: κοτυληδών kotylēdōn, from κοτύλη ''kotýlē'', "cup bowl" Once the embryo begins to germinate — grow out from the seed — it is called a seedling. Germination is the process whereby growth emerges from a period of dormancy Plants that do not produce seeds, but do produce an embryo, include the bryophytes and ferns. Bryophytes are all Embryophytes ('land Plants) that are non-vascular: they have tissues and enclosed reproductive systems but they lack Vascular tissue A fern is any one of a group of about 20000 Species of Plants classified in the phylum or division Pteridophyta, also known as Filicophyta In these plants, the embryo is a young plant that grows attached to a parental gametophyte. In Plants and Algae that undergo Alternation of generations, a gametophyte is the multicellular structure or phase that is Haploid, containing
- 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. See also Evolution of mammals Eutheria ("true beast" are a group of Mammals consisting of Placental mammals plus all extinct Mammals Cell division is a process by which a cell, called the parent cell divides into two or more cells called daughter cells. For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" An ovum (plural ova) is a Haploid Female reproductive cell or Gamete. A fetus (or foetus or fœtus) is a developing Mammal or other Viviparous Vertebrate, after the Embryonic stage and In humans, the embryo is defined as the product of conception from implantation in the uterus through the eighth week of development. The uterus (from the Latin word for womb) is the major Female reproductive organ of most Mammals including Humans One end the An embryo is called a fetus at a more advanced stage of development and up until birth or hatching. Childbirth (also called labour, birth, partus or parturition) is the culmination of a Human Pregnancy or In humans, this is from the eighth week of gestation. Gestation is the carrying of an Embryo or Fetus inside a Female Viviparous Animal.
The human embryo
Growth
- 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). Human embryogenesis is the process of Cell division and Cellular differentiation of the human Embryo during early Prenatal development. Prenatal development is the process in which an embryo or fetus (or foetus) gestates during Pregnancy, from fertilization The endometrium is the inner membrane of the Mammalian Uterus. When it comes into contact with the endometrium it performs implantation. Implantation is an event that occurs early in pregnancy in which the Embryo adheres to the wall of Uterus. Implantation connections between the mother and the embryo will begin to form, including the umbilical cord. In placental Mammals the umbilical cord (also called the birth cord or funiculus umbilicalis) is the connecting cord from the developing Embryo 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. [2]
Week 4-5 Chemicals produced by the embryo stop the woman's menstrual cycle. The menstrual cycle is a recurring cycle of physiologic changes that occurs in reproductive-age Females Overt menstruation (where there is blood flow from the Neurogenesis is underway, showing brain activity at about the 6th week. 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. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object The brain develops into five areas. Tissue formation occurs that develops into the vertebra and some other bones. The heart starts to beat and blood starts to flow. [2]
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. A fetus (or foetus or fœtus) is a developing Mammal or other Viviparous Vertebrate, after the Embryonic stage and [2]
Status
The status of the human embryo is debated by some bioethicists. Bioethics is the philosophical study of the ethical controversies brought about by advances in Biology and Medicine. Some Christian Ethicists believe that an embryo does, in fact, possess personhood. The term person is used in Common sense to mean an individual Human being. 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. Valparaiso University, known Colloquially as Valpo, is a private University located in the city of Valparaiso in the U "[3] The NIH defines the embryonic stage as the beginning of developed human form [2]
Footnotes
- ^ Gould, Stephen. "NIH" redirects here For other meanings of NIH see NIH (disambiguation. Ontogeny and Philogeny, page 206 (1977): "recapitulation was not 'disproved'; it could not be, for too many well-established cases fit its expectations. "
- ^ a b c d NIH Medical Encyclopedia http://www.nlm.nih.gov/medlineplus/ency/article/002398.htm
- ^ Gilbert Meilander, Bioethics: A Primer for Christians (2nd ed. ; Grand Rapids: Eerdmans, 2005), p. 29.
See also
- Embryogenesis
- Embryology
- In vitro fertilization
- Plant embryogenesis
- Embryo space colonization
- Pregnancy
- Embryo adoption
- Sexual
- Prenate
| Preceded by Zygote |
Stages of human development Embryo |
Succeeded by Fetus |
External links
- Chart of human fetal development
- A Comparative Embryology Gallery
- Development of the human embryo
- The Visible Embryo from fertilization to birth
- The Human Fertilisation and Embryology Authority (HFEA)
- The Developing Human (Keith L. Embryogenesis is the process by which the Embryo is formed and develops Embryology (from Greek grc ἔμβρυον embryon, "unborn embryo" and grc -λογία -logia) is the study of the development In vitro fertilisation ( IVF) is a process by which Plant embryogenesis is the process that produces a plant embryo from a fertilised ovule by asymmetric cell division and the differentiation of undifferentiated cells into tissues and Embryo space colonization is a Theoretical interstellar Space colonization concept that involves sending a robotic mission to a habitable Terrestrial Pregnancy ( Latin graviditas) is the carrying of one or more offspring known as a Fetus or Embryo, inside the Uterus of a Female Embryo donation is a form of Third party reproduction. In vitro fertilisation often results in a number of frozen unused embryos after the woman for whom they were Generally speaking human sexuality is how people experience and express themselves as sexual beings Prenatal development is the process in which an embryo or fetus (or foetus) gestates during Pregnancy, from fertilization For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" Human development is the process of Growing to maturity In biological terms this entails growth from a one-celled Zygote to an adult Human being A fetus (or foetus or fœtus) is a developing Mammal or other Viviparous Vertebrate, after the Embryonic stage and Moore) http://www.youtube.com/watch?v=Rb0uZefwQnc
Dictionary
embryo
-noun
- An unborn baby that is less developed than a foetus.
- An organism in the earlier stages of development before it emerges from the egg, or before metamorphosis.
- In viviparous animals, the young animal's earliest stages in the mother's body
- In humans, usually the cell growth up to the end of the seventh week in the mother's body
- (botany) A rudimentary plant contained in the seed.
- The beginning; the first stage of anything.
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