blastula blas·tu·la (blās'chə-lə)
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.
|blastula (blās'chə-lə) Pronunciation Key
Plural blastulas or blastulae (blās'chə-lē')
An animal embryo at the stage immediately following the division of the fertilized egg cell, consisting of a ball-shaped layer of cells around a fluid-filled cavity known as a blastocoel. Compare gastrula. See also blastocyst.
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).
Note: This is the stage of development where embryonic stems cells can be harvested for medical research.