Final answer:
During embryonic development, mitosis occurs to create a multitude of cells, and differentiation happens to specialize these cells into three germ layers: ectoderm, mesoderm, and endoderm, which give rise to various organs and tissues in the body.
Step-by-step explanation:
Embryonic Development and Differentiation:
During the development of an embryo, both mitosis and differentiation occur. Mitosis is responsible for the rapid cell division of the zygote, or fertilized egg, resulting in many cells that form the embryo. This type of cell division is necessary to produce genetically identical cells in the developing fetus.
As the embryo develops, the inner cell mass of the blastocyst, also called the embryoblast, differentiates into two groups of cells known as the epiblast and the hypoblast which eventually form a two-layered embryonic disc. During the second week after fertilization, a process called gastrulation occurs, which yields three germ layers: the ectoderm, mesoderm, and endoderm. These germ layers are critical for the differentiation process, as cells become specialized to form different tissues and organs of the human body.
The ectoderm layer will give rise to the skin and nervous system cells. The mesoderm layer develops into cells of organs such as the bones, muscles, and heart. The innermost layer, the endoderm, will eventually become the cells of most internal glands and organs. Ultimately, the embryonic stage characterized by a fluid-filled cavity with an inner cell mass surrounded by a layer of cells is known as the blastocyst.