It occurs in the same way as in the equator, where part of the acetoderm on the fair line of the dorsal region of the embryo begins to thicken and differentiate into a particular type of cell. This is known as the flat segment, which is enlarged by the nerve plate, and whose flanks tend to rise up and the flattened part falls into a low groove known as the nervous cavity Its high extremities are the two nerve bends and with the growth continuing, the nerve plate decreases. The two interstitial ligaments approach each other until the extremities join and the nerve plate is covered with a layer of the actoderm cells. A complete tube with a central cavity known as the neural canal and above which the acetoderm is completely covered. And the process of fusion of the nerve folds and the neural tube does not start from the forefront, but from a point slightly away from the front of the fetus near the location of the rectum and rectangle from this place moves docking to the back where the nerve tube and forward where the brain is composed of different parts and from the beginning of the differentiation of the nervous acetoderm until the end of composition Neural tube The fetus is called the Nerula, where the fetus becomes extinct and becomes white.
