neural tube

The neural tube is the simple, hollow tube of cells that an embryo builds very early on, and it is the seed from which the entire brain and spinal cord will grow. Picture a flat sheet of paper laid on a table: now imagine its two long edges lifting up, curling toward each other, and zipping shut along the middle to form a hollow drinking straw. That is roughly what happens in a developing embryo — a flat patch of cells on the back, called the neural plate, folds up and seals into a closed tube. Everything that later becomes your thoughts, senses, and movements begins as this one humble structure.

Once the tube is sealed, its two ends take on different jobs. The front end balloons out and divides into bulges that become the brain, while the long, narrow stretch behind it becomes the spinal cord — the cable of nerves running down your back. The hollow space inside the tube never disappears: it stays as the fluid-filled channels and chambers that thread through the adult brain and spinal cord. Because so much depends on the tube folding and closing cleanly, this is a delicate moment. If part of it fails to zip shut, the result is a neural tube defect such as spina bifida, which is one reason pregnant people are advised to get enough folic acid, a vitamin that helps the tube close properly.