During early embryonic development, the solid ball of cells before the blastocyst forms is known as:

During early embryonic development, the solid ball of cells before the blastocyst forms is known as:

• A. Zygote
• B. Morula
• C. Blastocyst
• D. Gastrula

Answer: (B)

The solid ball of cells formed after several cleavages of the zygote is called the morula. It arises as rapid cell divisions produce many small cells (blastomeres) without growth in size, creating a compact, uniform mass. This stage is solid because there’s no hollow cavity yet. Soon after, a fluid-filled cavity forms to create the blastocyst, which is why the morula is distinguished from the hollow blastocyst stage. For context, the zygote is the fertilized egg, the blastocyst has a cavity and inner cell mass, and gastrulation happens later to form the germ layers.

The solid ball of cells formed after several cleavages of the zygote is called the morula. It arises as rapid cell divisions produce many small cells (blastomeres) without growth in size, creating a compact, uniform mass. This stage is solid because there’s no hollow cavity yet. Soon after, a fluid-filled cavity forms to create the blastocyst, which is why the morula is distinguished from the hollow blastocyst stage. For context, the zygote is the fertilized egg, the blastocyst has a cavity and inner cell mass, and gastrulation happens later to form the germ layers.