The pre-embryo becomes a hollow ball of cells with a fluid-filled cavity by about day 6 of development. This stage is called a ________.
A) blastocoel
B) morula
C) blastula
D) blastocyst

Question

Quizplus · Accepted Answer

The stage described in the question is that of a blastocyst, which occurs around day 6 of development. The blastocyst has a hollow cavity filled with fluid and is made up of an outer layer of cells (called the trophoblast) and an inner cell mass that will eventually give rise to the embryo itself. The other options (A, B, and C) describe earlier stages of development.

The Pre-Embryo Becomes a Hollow Ball of Cells with a Fluid-Filled