This week your baby begins to grow rapidly and will become much more recognizable as a baby over the next five weeks. There are three types of cell, each committed to a separate function. The first will form the skin and nervous system; the second forms blood vessels, muscles, and bones; the third forms the entire digestive system.
At this stage, it is the cells responsible for the spine and nervous system that are at work. Changing shape from a flat disk, the embryo starts to curl up. The edges of the groove that has already partially formed along the back gradually start to meet, closing and fusing to form a tube, which will become the brain and spinal cord. The last parts of the tube to close are at the very top of the head and then the base of the spine, two days later.
Being careful to get an adequate intake of folic acid in early pregnancy is essential to ensure the neural tube closes completely, with no gaps.