Neurulation is the process of forming the neural tube during early embryonic development in vertebrates. It is a crucial step in the development of the central nervous system, as it leads to the formation of the brain and spinal cord. Neurulation begins in the third week of embryonic development and is completed in the fifth week. During this process, a flat sheet of cells called the neural plate is transformed into a hollow tube, which ultimately forms the neural tube. This tube is composed of three distinct layers, each of which has a different role in the development of the nervous system. In this article, we will discuss the process of neurulation, its different stages, and the components involved in the process.
Neurulation begins with the folding of the neural plate to form the neural groove. The two edges of the neural plate come together to form the neural folds, which eventually fuse together to form the neural tube. During this process, different cell types are involved, which are responsible for the folding and fusion of the neural plate. These cell types include the neural crest cells, which secrete molecules that cause the cells to migrate and move towards the midline of the neural plate. In addition, the epidermal cells secrete a protein called E-cadherin, which allows the cells to adhere to each other and form the neural tube.
Once the neural tube has formed, further development takes place through the process of neurulation. During the second stage, the neural folds begin to elongate and the neural tube begins to form a lumen. This lumen is filled with cerebrospinal fluid and is responsible for the development of the brain and spinal cord. At the same time, the neural crest cells migrate and differentiate into neurons and glia. Neurons migrate to different regions of the brain and spinal cord, where they develop into different types of nerve cells. Glia, on the other hand, provide support and insulation to the neurons.
The third stage of neurulation is the differentiation of the neural tube into the three layers, known as the ectoderm, mesoderm, and endoderm. The ectoderm gives rise to the outermost layer of the neural tube, which forms the skin, nervous system, eyes, and ears. The mesoderm is responsible for the formation of the skeletal muscles, connective tissues, and the circulatory system. Finally, the endoderm forms the innermost layer of the neural tube, which will later give rise to the digestive system.
In conclusion, neurulation is a complex process involving many different cell types and components. It is an essential step in the development of the central nervous system, as it leads to the formation of the brain and spinal cord. Through this process, the neural plate is transformed into a hollow tube, which is composed of three distinct layers. Further development of the neural tube then occurs through the process of differentiation, which forms the various components of the nervous system.
References:
Houart, C., & Wilson, S. W. (2017). The making of the nervous system: from neural plate to neural tube. Developmental Biology, 424(2), 125-135.
Rosenquist, G. (2011). Neurulation: The formation of the neural tube. Developmental Dynamics, 240(11), 2362-2373.
Takahashi, T., & Yost, H. J. (1996). Neurulation in vertebrates: A multipotent view. Developmental Biology, 178(2), 304-320.