Optometry Admission Test (OAT) Practice

What structure is primarily formed through the ectoderm?

1. Respiratory system

2. Nervous system

3. Muscular system

4. Endocrine system

The correct answer is: Nervous system

The correct choice highlights the role of the ectoderm, which is one of the three germ layers formed during embryonic development. The ectoderm is primarily responsible for giving rise to structures involved in the nervous system. This includes the brain and spinal cord, as well as peripheral nerves. Additionally, components such as the epidermis and sensory organs (like the eyes and ears) also develop from the ectoderm. In contrast, the other systems listed originate from different germ layers. The respiratory system is mainly derived from the endoderm, which also gives rise to the gastrointestinal tract and associated organs. The muscular system develops from the mesoderm, which is responsible for forming muscles, bones, and the cardiovascular system. Lastly, the endocrine system has contributions from both the ectoderm and mesoderm but is primarily associated with structures like the thyroid and adrenal glands, which have endodermal origins. This distinction in germ layer origins is fundamental in understanding embryology and the development of various organ systems.