Which term denotes the fluid-filled central cavity within a blastocyst?

Which term denotes the fluid-filled central cavity within a blastocyst?

• A. Blastocyst
• B. Blastocoele
• C. Blastomere
• D. Cleavage stage embryos

Answer: (B)

The fluid-filled central cavity is called the blastocoel (also spelled blastocoele). During blastulation, the solid mass formed by cleavage hollows out and fills with fluid, creating this cavity. The blastocyst then forms around it, with the outer trophoblast and the inner cell mass sitting beside the cavity. This cavity is what allows the embryo to expand and later differentiate as implantation proceeds. The other terms refer to different structures or stages: a blastocyst is the whole hollow embryo, a blastomere is an individual cell produced by cleavage, and cleavage stage embryos describe the earlier division phase before the blastocyst forms.

The fluid-filled central cavity is called the blastocoel (also spelled blastocoele). During blastulation, the solid mass formed by cleavage hollows out and fills with fluid, creating this cavity. The blastocyst then forms around it, with the outer trophoblast and the inner cell mass sitting beside the cavity. This cavity is what allows the embryo to expand and later differentiate as implantation proceeds. The other terms refer to different structures or stages: a blastocyst is the whole hollow embryo, a blastomere is an individual cell produced by cleavage, and cleavage stage embryos describe the earlier division phase before the blastocyst forms.