Optometry Admission Test (OAT) Practice

Which of the following describes the primary outcome of gastrulation?

1. The formation of the embryo

2. Development of the three primary germ layers

3. The establishment of the placenta

4. The differentiation of tissues into organs

The correct answer is: Development of the three primary germ layers

The primary outcome of gastrulation is best described by the development of the three primary germ layers: ectoderm, mesoderm, and endoderm. This critical process occurs early in embryonic development after the blastula stage and sets the foundation for the organization of the body plan. During gastrulation, cells undergo extensive movements, invaginating and migrating to form the three layers. The ectoderm will ultimately give rise to the skin and nervous system, the mesoderm will form structures such as muscles, bones, and circulatory systems, while the endoderm will develop into the gastrointestinal tract and internal organs. Understanding gastrulation is crucial as it is the stage in which the embryo transitions from a simple structure into a more complex organization, where the groundwork for all subsequent development is laid. This significant transformation greatly influences the formation of tissues and organs in later developmental stages.