a hollow ball of cells. novaNET
a hollow ball of cells. novaNET
it is called a blastocyst
A blastula typically consists of a single layer of cells called the blastoderm. This layer forms during early embryonic development and surrounds a fluid-filled cavity called the blastocoel.
The primary germ layers (endoderm, mesoderm, and ectoderm) are formed and organized in their proper locations during gastrulation. Endoderm, the most internal germ layer, forms the lining of the gut and other internal organs. Ectoderm, the most exterior germ layer, forms skin, brain, the nervous system, and other external tissues. Mesoderm, the the middle germ layer, forms muscle, the skeletal system, and the circulatory system.