Illustration of blastula
- c blastocoel
- ma macromere
- mi micromere
- a animal pole
- v vegetal pole
blastula
noun
blas·tu·la ˈblas-chə-lə 
plural blastulas or blastulae ˈblas-chə-ˌlē
: an early metazoan embryo typically having the form of a hollow fluid-filled rounded cavity bounded by a single layer of cells compare gastrula, morula
blastulation
ˌblas-chə-ˈlā-shən
noun 
Word History
Etymology
borrowed from New Latin (in a German context), from Greek blastós "shoot, bud, embryo" + New Latin -ula (as in gastrula, planula) — more at -blast
Note: Term apparently introduced by the Russian zoologist and embryologist Vladimir Vladimirovič Zalenskij ("W. Salensky," 1847-1918) in "Bemerkungen über Haeckel's Gastraea-Theorie," Archiv für Naturgeschichte, 40. Jahrgang, 1. Band (1874), p. 162.
First Known Use
1875, in the meaning defined above
Medical Definition
blastula
noun
blas·tu·la ˈblas-chə-lə
plural blastulas or blastulae -ˌlē
: an early metazoan embryo typically having the form of a hollow fluid-filled rounded cavity bounded by a single layer of cells compare gastrula, morula