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Encyclopedia > Primitive streak
Embryology: Primitive streak
Surface view of embryo of a rabbit.
arg. Embryonic disk.
pr. Primitive streak.
Latin '
Gray's subject #6 47
Carnegie stage 6b
Days {{{Days}}}
Gives rise to
MeSH A16.254.412
Dorlands/Elsevier s_25/12761719

The primitive streak is a structure that forms during the early stages of avian, reptilian and mammalian embryonic development. The formation of the primitive streak is one of the first signs of gastrulation. It is characterized as a furrow in the midline of the embryonic disk at the future caudal end of the embryo. This furrow is formed by the ingression of epiblast cells which will go on to form the definitive endoderm and mesoderm by replacing hypoblast cells. Embryos (and one tadpole) of the wrinkled frog (Rana rugosa). ... Genera Pentalagus Bunolagus Nesolagus Romerolagus Brachylagus Sylvilagus Oryctolagus Poelagus Rabbits are small mammals in the family Leporidae, found in many parts of the world. ... Latin is an ancient Indo-European language. ... In biology, an organ is a group of tissues which perform some function. ... In embryology, Carnegie stages are a standardized system of 23 stages used to provide a unified developmental chronology of the embryo. ... Embryology is the branch of developmental biology that studies embryos and their development. ... Embryology is the branch of developmental biology that studies embryos and their development. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... Elseviers logo Elsevier, the worlds largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. ... The word Avian can refer to different things: .. Most commonly it is used referring to the class of animals named birds. Avians are a fantasy race in several fantasy settings. ... Orders  Crocodilia - Crocodilians scary crocodiles. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... Embryogenesis is the process by which the embryo is formed and develops. ... 1 - blastula, 2 - gastrula; orange - ectoderm, red - endoderm. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... In embryology, the epiblast is a feature present during gastrulation. ... The endoderm, sometimes refered to as entoderm, is one of the three germ layers of the developing embryo, the other two being the ectoderm and the mesoderm. ... The mesoderm is one of the three germ layers in the early developing embryo, the other two layers being the ectoderm and the endoderm. ...

The primitive streak establishes a visible longitudinal axis of bilateral symmetry around which all embryonic structures will organize and align. The primitive streak consists of the following: In biology, bilateral symmetry is a characteristic of multicellular organisms, particularly animals. ...

  • Primitive groove - shallow valley extending along the length of the streak.
  • Primitive node - a raised circle of cells at the rostral tip of the primitive streak. (Hensen's node)
  • Primitive pit - a depression in the center of the primitive node.



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