Optometry Admission Test (OAT) Practice

Which embryonic stage involves cell differentiation leading to tissue and organs?

1. Implantation

2. Blastulation

3. Gastrulation

4. Neurulation

The correct answer is: Gastrulation

During the embryonic development process, gastrulation is the pivotal stage that involves significant cellular differentiation and the establishment of germ layers, which ultimately give rise to various tissues and organs in the body. In gastrulation, the inner cell mass of the blastocyst reorganizes to form three primary germ layers: ectoderm, mesoderm, and endoderm. Each of these layers develops into different systems and structures: the ectoderm becomes the skin and nervous system, the mesoderm forms muscles, bones, and the circulatory system, while the endoderm develops into the gastrointestinal tract and associated organs. Understanding this process is vital for comprehending how complex structures and systems in the body are formed from a relatively simple grouping of cells. This differentiation sets the stage for subsequent development and specialization of tissues and organs, which is crucial for the organism's growth and functionality. Other stages mentioned, such as implantation, blastulation, and neurulation, have their own roles in development but do not center specifically on the initial differentiation into the primary tissue layers that occurs during gastrulation.