Certificate In Psychology (CPSY) Practice Exam

What is the outer layer of cells in early embryonic development called?

1. Ectoderm

2. Endoderm

3. Mesoderm

4. Chorion

The correct answer is: Ectoderm

The outer layer of cells in early embryonic development is referred to as the ectoderm. This germ layer plays a critical role in the formation of various structures and systems in the developing embryo, including the skin, nervous system, and sense organs. During the process of gastrulation, the embryo develops three primary germ layers: ectoderm, mesoderm, and endoderm. The ectoderm is crucial because it gives rise to tissues that form protective outer shields and facilitate interaction with the environment. Understanding the role of the ectoderm is essential for grasping how different body systems and organs develop as the embryo matures. Other options like endoderm and mesoderm represent different germ layers that develop into other organs and systems; the endoderm primarily forms internal structures such as the digestive and respiratory systems, while the mesoderm gives rise to muscles, bones, and the circulatory system. The chorion, on the other hand, is an extra-embryonic structure involved in nutrient exchange and the formation of the placenta, but it is not classified as one of the three primary germ layers.