Medical College Admission Test (MCAT) Practice Exam 2026 - Free MCAT Practice Questions and Study Guide

The ectoderm is the correct answer as it plays a crucial role in the development of the nervous system. Early in embryonic development, the ectoderm is the outermost layer of the three primary germ layers: ectoderm, mesoderm, and endoderm. The nervous system originates from a specialized region of the ectoderm known as the neuroectoderm.

During the process of neurulation, the ectoderm forms the neural plate, which subsequently folds to create the neural tube. The neural tube eventually develops into the brain and spinal cord, key components of the central nervous system. Additionally, the ectoderm gives rise to other structures in the nervous system, such as peripheral nerves and certain sensory structures.

The involvement of mesoderm and endoderm in other developmental processes, such as the formation of muscles, bones, and internal organs, highlights the distinct roles each germ layer plays during development. However, the direct contribution to the formation of the nervous system is solely attributed to the ectoderm.