Question

At 3 weeks or so after conception, cells making up the tube differentiate into a mass of neurons, most of which then develop into three major regions of the brain:

Answer 1

Neurulation is a critical developmental process that leads to the formation of the brain and spinal cord, with the neural tube differentiating into three primary regions - the forebrain, midbrain, and hindbrain, which further develop into the collective structures of the adult brain.

Step-by-step explanation:

Development of the Brain from the Neural Tube

The process of neurulation, which takes place approximately three to four weeks after fertilization, is critical for the formation of the central nervous system in an embryo. During this period, the neural plate, comprised of specialized neuroectodermal tissues, begins to fold inwards forming the neural tube, which lies atop the notochord. This neural tube will eventually differentiate into the brain and spinal cord - the core components of the nervous system.

Formation of Brain Regions

During the fourth week of development, the anterior portion of the neural tube starts differentiating into three primary vesicles - the forebrain, midbrain, and hindbrain. These vesicles further subdivide, resulting in complex structures aligned with the major regions of the adult brain. Specifically, the forebrain evolves into the cerebrum and diencephalon, the midbrain remains as the mesencephalon, the hindbrain divides into the metencephalon develops into the cerebellum and the myelencephalon becomes part of the brain stem.