early stage of an embryo produced by cleavage of an ovum; a liquid-filled sphere whose wall is composed of a single layer of cells; during this stage (about eight days after fertilization) implantation in the wall of the uterus occurs
例句
用作名词(n.)
The cells of the blastula, called blastomeres, also each receive a full diploid set of chromosomes.这些囊胚细胞，称卵裂球，每个细胞都有一套二倍体染色体组。
Cleavage produces a blastula, a sheet of cells rounded into a sphere that in most species surrounds a cavity.卵裂产生一个囊胚，形成的细胞壁球形排列形成一个空腔。
