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n. pl. blas·tu·las or blas·tu·lae (-lē′)
An early embryonic form produced by cleavage of a fertilized ovum and consisting of a spherical layer of cells surrounding a fluid-filled cavity. Also called blastosphere.

[New Latin : from Greek blastos, bud + Latin -ula, feminine diminutive suff.]

blas′tu·lar adj.
blas′tu·la′tion (-lā′shən) n.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


(Biology) embryol the process of blastula formation
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
References in periodicals archive ?
In general, the competence of oocyte is evaluated by maturation rate, fertilization rate, cleavage rate and blastulation ratio (Iwata et al., 2004).
This embryo had the expected annotation (according to the producer model) with first division at 24.7 h and start blastulation at 114 h (Figure 2).
(14) Oocytes from women with a BMI >25 kg/[m.sup.2] are smaller and less likely to complete development postfertilization, with embryos arrested prior to blastulation containing more triglyceride than those forming blastocysts.
Indeed, the induction of as few as three to six concurrent stimulated ovulatory cycles has been shown to elicit increased mitochondrial aggregation and mitochondrial DNA (mtDNA) mutations in oocytes, as well as oxidative damage to nuclear DNA, lipids, and proteins--lesions that collectively result in degenerative embryos and failure to reach blastulation [42].
Laegdsmand, "Aneuploidy is a key causal factor of delays in blastulation: author response to "A cautionary note against aneuploidy risk assessment using timelapse imaging"," Reproductive BioMedicine Online, vol.
The continuous monitoring of the progress of the embryo development is possible by following the key indicators of this process (both positive and negative) such as formation of the pronucleus, early cleavage, cell cycle intervals, synchronization of cell division and initiation of blastulation, and multinucleation, etc., since all these contribute to the selection of the best embryos for transfer [11].
Both genomic DNA and mitochondrial DNA in spent medium were significantly correlated with fragmentation rate, one of the morphologic parameters conventionally used for assessing embryo quality, and mitochondrial DNA mirrored the blastulation potential of both fragmented and high-grade embryos.