A second set of hinge points are formed dorsolaterally at more caudal levels of the spinal neuraxis, the dorsolateral hinge points (DLHPs), a process that appears to enhance the ability of the apposing tips of the neural folds to come close to each other (Figure 3(c)). Mode 2 occurs during formulation of the spinal neural tube in 12–15-somite stage embryos and generates a diamond-shaped lumen, as depicted in Figures 4(c) and 4(d). In Mode 2, a median hinge point is also present, whereas the remaining portions of the neuroepithelium do not bend. At the 17–27-somite stage, the neural tube closes without a median hinge point, whereas dorsolateral hinge points are retained. This is known as Mode 3 neurulation and generates an almost circular shaped lumen, as shown in Figures 4(e) and 4(f).