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blastula vs. blastocyst

blastula
[blas-chuh-luh] / ˈblæs tʃə lə /

noun

Embryology.
blastulas, plural blastulae plural

  1. the early developmental stage of an animal, following the morula stage and consisting of a single, spherical layer of cells enclosing a hollow, central cavity.

blastocyst
[blas-tuh-sist] / ˈblæs tə sɪst /

noun

Embryology.

  1. the blastula of the mammalian embryo, consisting of an inner cell mass, a cavity, and an outer layer, the trophoblast.