| A | B |
|---|
| Embryo | In the early stages of development, the organism is called an |
| Cleavage | A series of mitotic divisions where the embryo increases in cell number but NOT in cell size |
| Blastula | As cleavage continues, the cells form a hollow ball-type structure filled with fluid called a |
| Gastrula | Once the blastula forms, the cells of the inner cell mass push in and form a three-layered embryo called the |
| Gastrulation | The process in which a blastula forms into a three-layered embryo is known as |
| Differentiation | A series of changes that transform the unspecialized embryonic cells into specialized cells, tissues and organs |
| Growth | The term defined as not only are the number of cells increasing, but the size of the cells are increasing as well, and the embryo as a whole starts to develop |
| Fertilization | The proces that causes the developmental genes to begin their functions |
| Morula | A 32 cell embryo that is still trapped inside the zona |
| Inner cell mass | The part of the blastula that will become the organism itself |
| Blastocoel | A hollow that forms in the c enter of the developing blastula |
| Primitive streak | A hole or furrow that forms on the blastula to begin gastrulation |
| Placenta | Provides nourishmant and the oxygen for the developing embryo |
| Umbilical cord | attaches the embryo to the placenta |
| Neurulation | The process that forms the first permanent structure in the embryo |
| Ectoderm | Gives rise to the nervous system and skin |
| Endoderm | Gives rise to the lining of the digestive tract and organs like the liver |
| Mesoderm | Gives rise to bones and muscles |
| Neural tube | One end of this structure will develop into the brain, the other into the spinal cord |
| Organogenesis | The longest stage of embryonic development |
