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American Heritage Dictionary:
blas·tu·la |
[New Latin : from Greek blastos, bud + Latin -ula, feminine diminutive suffix.]
blastular blas'tu·lar adj.|
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McGraw-Hill Science & Technology Encyclopedia:
Blastulation |
The formation of a segmentation cavity or blastocoele within a mass of cleaving blastomeres and rearrangement of blastomeres around this cavity in such a way as to form the type of definitive blastula characteristic of each species. The blastocoele originates as an intercellular space which sometimes arises as early as the four- or eight-cell stage. Thus blastulation is initiated during early cleavage stages, and formation of the definitive blastula is thought to terminate cleavage and to initiate gastrulation. Initially the diameter of the blastula is no greater than that of the activated egg; subsequently it increases. See also Gastrulation.
The blastula is usually a hollow sphere. Its wall may vary from one to several cells in thickness. In eggs which contain considerable amounts of yolk the blastocoele may be eccentric in position, that is, shifted toward the animal pole. The animal portion of its wall is always completely divided into relatively small cells, whereas the vegetative portion tends to be composed of relatively large cells and may be incompletely cellulated in certain species. The blastocoele contains a gelatinous or jellylike fluid, which originates in part as a secretion by the blastomeres and in part by passage of water through the blastomeres or intercellular material, or both, into the blastocoele.
The wall of the blastula is a mosaic of cellular areas, each of which will normally produce a certain structure during subsequent development. In other words, each area of cells in the wall of the blastula has a certain prospective fate which will be realized in normal development.
Dictionary of Cultural Literacy: Science:
blastula |
The stage of an embryo that consists of just over a hundred cells — a stage reached about one week after fertilization. At this stage the cells are just at the very beginning of cellular differentiation and are said to be totipotent (See totipotency).
Saunders Veterinary Dictionary:
blastulation |
Conversion of the morula to the blastula by development of a blastocele.
Random House Word Menu:
categories related to 'blastula' |
Wikipedia on Answers.com:
Blastula |
| Blastula | |
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| Blastulation: 1 - morula, 2 - blastula. | |
| Days | 4 |
| Precursor | Morula |
| Gives rise to | Gastrula |
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The blastula (from Greek βλαστός (blastos), meaning "sprout") is a hollow sphere of cells formed during an early stage of embryonic development in animals [1]. The blastula is created when the zygote undergoes the cell division process known as cleavage.[2] The blastula is preceded by the morula and is followed by the gastrula in the developmental sequence.[citation needed]
A common feature of a vertebrate blastula is that it consists of a layer of blastomeres, known as the blastoderm, which surrounds an interior central cavity known as the blastocoel.[3] [4] In mammals, blastulation leads to the formation of the blastocyst, which must not be confused with the blastula. The blastocyst contains an embryoblast, which is homologous to the blastula. However, it also includes the trophoblast, which goes on to form the extraembryonic tissues.[citation needed]
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This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
 | blastomere (embryology) |
| blastocele |
| blastoderm |
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Copyrights:
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 | American Heritage Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| McGraw-Hill Science & Technology Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| Dictionary of Cultural Literacy: Science. The New Dictionary of Cultural Literacy, Third Edition Edited by E.D. Hirsch, Jr., Joseph F. Kett, and James Trefil. Copyright © 2002 by Houghton Mifflin Company. Published by Houghton Mifflin. All rights reserved. Read more |
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| Saunders Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more |
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| Random House Word Menu. © 2010 Write Brothers Inc. Word Menu is a registered trademark of the Estate of Stephen Glazier. Write Brothers Inc. All rights reserved. Read more |
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| Wikipedia on Answers.com. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article Blastula. Read more |
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