31. It is distinct from the mesoderm underneath the neural tube which is called the chordamesoderm that becomes the notochord . 32. Through the process of neurulation, the notochord induces the formation of the neural tube in the embryonic disc. 33. The notochord secretes BMP antagonists ( Chordin and Noggin ) to prevent formation of cardiac mesoderm in inappropriate places. 34. The paraxial mesoderm is arranged along the sides of the notochord and neural tube as repetitive structures called somites. 35. The notochord expresses SHH . The floor plate responds to SHH by producing its own SHH and forming a gradient. 36. Amphioxus forms an epithelial neural tube and dorsal notochord but does not have the EMT potential of the primitive streak. 37. Noggin was also shown to be indirectly involved in the malformations through its interaction with the notochord and neural axis. 38. During the third week of gestation the notochord sends signals to the overlying ectoderm, inducing it to become neuroectoderm. 39. Flexion ( the bending of the notochord as part of caudal fin formation ) occurs at around a length of. 40. The secretion of SHH by the notochord establishes the ventral pole of the dorsal-ventral axis in the developing embryo.
