Did you know that the brain is formed from the same embryological layer as the skin? And that it's shaped like a cylinder during the first stages of life? Like all other organs and tissue, the most complex organ in our body and source of our thoughts and emotions, comes from a single cell formed by the fertilization of an ovum by a sperm cell. Let's take a closer look at brain development for the sheer sake of satisfying our curiosity about this mysterious organ.

At the beginning, the embryo is little more than an elongated mass of cells. But even at this early stage, through successive multiplications and differentiations, these three layers of cells will one day become the tissues and organs that compose the entire organism. From inside to outside, these three layers are known as the endoderm, mesoderm, and ectoderm. The first two layers will become the intestines, lungs, bones and muscles, while the outermost layer, or ectoderm, will develop into the epidermis (the outermost layer of the skin) and nervous system.

Neurulation begins at this stage with the formation of the nervous system. It begins very early, often even before the mother knows she is pregnant. At 19 days after fertilization, the nervous system consists of a single disc called the neural plate. This plate will first fold itself inward to form the neural groove and then close completely to form the neural tube. Imagine holding a sheet of paper in your hand and gradually moving your hands together. The sheet begins to sag in the middle to form a U shape, and then forms a cylindrical tube once your hands touch. But the tube doesn't close all at once; the middle comes together first and then continues toward the two ends, closing like a zipper. Thirteen days later, the neural tube closes completely and separates from the ectoderm to lie beneath the surface. Located all along the embryo, the neural tube gives the fetus its characteristic curved shaped. Later, the brain and spinal cord will develop from this structure.

The next step involves a series of cell differentiations in the neural tube which creates three and then five subdivisions known from the rostral (head) to caudal (tail) end as the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon.

Stay tuned for more stages of brain development in our next newsletter.