FACTOID # 21: 15% of Army recruits from South Dakota are Native American, which is roughly the same percentage for female Army recruits in the state.
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Encyclopedia > Carnegie stages

In embryology, Carnegie stages are a standardized system of 23 stages used to provide a unified developmental chronology of the vertebrate embryo. Image File history File links This is a lossless scalable vector image. ... This article or section is in need of attention from an expert on the subject. ... Classes and Clades See below Male and female Superb Fairy-wren Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns. ... It has been suggested that embryology be merged into this article or section. ...

The stages are delineated through the development of structures, not by size or the number of days of development, and so the chronology can vary between species, and to a certain extent between embryos. It only covers the first 60 days of development; at that point the term embryo is usually replaced with the term fetus. It has been suggested that embryology be merged into this article or section. ... Human fetus at eight weeks. ...

It was based on work by Streeter (1942) and O'Rahilly and Müller (1987). The name "Carnegie stages" comes from the Carnegie Institute. The Carnegie Institution of Washington (CIW) is a foundation established by Andrew Carnegie in 1902 to support scientific research. ...

While the Carnegie stages provide a universal system for staging and comparing the embryonic development of most vertebrates, other systems are occasionally used for the common model organisms in developmental biology, such as the Hamburger-Hamilton stages in the chick. A model organism is a species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. ... Views of a Foetus in the Womb, Leonardo da Vinci, ca. ... In developmental biology, the Hamburger-Hamilton stages (HH) are a series of 46 chronological stages in chick development, starting from laying of the egg and ending with a newly hatched chick. ... This article or section does not adequately cite its references or sources. ...



Days are approximate, and reflect the days since the last ovulation before pregnancy ("Postovulatory age"). Ovulation is the process in the menstrual cycle by which a mature ovarian follicle ruptures and discharges an ovum (also known as an oocyte, female gamete, or casually, an egg) that participates in reproduction. ... A pregnant woman near the end of her term Pregnancy is the carrying of one or more embryos or fetuses by female mammals, including humans, inside their bodies. ...

Stage 1: 1 days

Categories: Biology stubs ... The Polar body is a cell structure found inside an ovum. ...

Stage 2: 3 days

In embryology, cleavage is the division of cells in the early embryo. ... Morula is a stage of embryonic development in animals, including the 16-cell phase, the 32-cell phase, and the 64-cell phase. ...

Stage 3: 4 days

The blastocyst is the structure formed in early mammalian embryogenesis, after the formation of the blastocele, but before implantation. ... A blastocoel(e) or blastocele or cleavage cavity or segmentation cavity is the central region of a blastocyst. ... The floor of the amniotic cavity is formed by the embryonic disk (or embryonic disc) composed of a layer of prismatic cells, the embryonic ectoderm, derived from the inner cell-mass and lying in apposition with the entoderm. ... The trophoblast (from Greek threphein: to feed) is considered to be the first of all embryonic annexes. ...

Stage 4: 5-6 days

Syncytiotrophoblasts are cells found in the placenta of human embryos. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... The ectoderm is outermost of the three germ layers of the developing embryo, the other two being the mesoderm and the endoderm. ...

Stage 5 (a-c): 7-12 days

Implantation occurs when a fertilized zygote attaches itself onto the lining of the uterus. ... The yolk sac is the first element seen in the gestational sac during pregnancy, usually at 5 weeks gestation. ... 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. ...

Stage 6: 13-15 days

The primitive streak is a structure that forms during the early stages of avian, reptilian and mammalian embryonic development. ... A shallow groove, the primitive groove, appears on the surface of the primitive streak, and the anterior end of this groove communicates by means of an aperture, the blastophore, with the yolk-sac. ... The chorion undergoes rapid proliferation and forms numerous processes, the chorionic villi, which invade and destroy the uterine decidua and at the same time absorb from it nutritive materials for the growth of the embryo. ... The yolk sac is the first element seen in the gestational sac during pregnancy, usually at 5 weeks gestation. ...

Stage 7: 15-17 days

1 - blastula, 2 - gastrula; orange - ectoderm, red - endoderm. ... The neural plate is thick and flat bundle of ectoderm which develops in the embryo into the nervous system. ... Haematopoiesis is the formation of blood cellular components. ... The notochord is a flexible, rod-shaped body found in embryos of all chordates. ...

Stage 8: 17-19 days

  • primitive pit

Stage 9: 19-21 days

Between the neural folds is a shallow median groove, the neural groove. ... In front of the primitive streak two longitudinal ridges, caused by a folding up of the ectoderm, make their appearance, one on either side of the middle line. ... The liver arises in the form of a diverticulum or hollow outgrowth from the ventral surface of that portion of the gut which afterward becomes the descending part of the duodenum. ... A placode is an area of thickening in the embryonic epithelial layer where some organ or structure later develops. ... The heart and lungs, from an older edition of Grays Anatomy. ...

Stage 10: 21-23 days

In the development of vertebrate animals, the branchial arches (or pharyngeal arches) develop during the fourth and fifth week in utero as a series of mesodermal outpouchings on the left and right sides of the developing pharynx. ... Intermediate mesoderm is a type of mesoderm that is located between the paraxial mesoderm and the lateral plate. ...

Stage 11: 23-26 days

Sinus venosus can refer to: Another name for the embryological structure Sinus venarum A type of atrial septal defect This is a disambiguation page: a list of articles associated with the same title. ... The Wolffian duct (also known as archinephric duct, Leydigs duct, and the mesonephric duct) is an organ found in humans during fetal development. ...

Stage 12: 26-30 days

  • upper limb buds

Stage 13: 28-32 days

The cavity of the primitive atrium becomes subdivided into right and left chambers by a septum, the septum primum, which grows downward into the cavity. ...

Stage 14: 31-35 days

The Ureteric bud is a portion of the mesonephric duct. ...

Stage 15: 35-38 days

Stage 16: 36-42 days

Stage 17: 42-44 days

Stage 18: 44-48 days

The septum secundum, semilunar in shape, grows downward from the upper wall of the atrium immediately to the right of the primary septum and foramen ovale. ...

Stage 19: 48-51 days

Stage 20: 51-53 days

Stage 21: 53-54 days

Stage 22: 54-58 days

Stage 23: 56-60 days

See also

Mammalian embryogenesis is the process of cell division and cellular differentiation which leads to the development of a mammalian embryo. ...

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