Development of Neural Tube and Somites (PDF)

04/11/23 Development of neural tube and somites and embryo folding: part 1: Learning objective: describe the process of neural tube formation, including four stages of neurulation. Neurulation: formation of the neural tube: This occurs in week 3 and 4. There are 4 main stages of neurulation: 1. Tran...

04/11/23 Development of neural tube and somites and embryo folding: part 1: Learning objective: describe the process of neural tube formation, including four stages of neurulation. Neurulation: formation of the neural tube: This occurs in week 3 and 4. There are 4 main stages of neurulation: 1. Transformation of the general ectoderm into a thickened neural plate. 2. Shaping of the plate so that it becomes narrower and longer. 3. Lateral folding of the neural plate into neural folds. 4. Fusion of the t wo most lateral apical surfaces of the neural folds into an autonomous neural tube. Day 18-21: Neural plate is a thickening of the ectoderm. As the notochord ( derived from mesoderm ) elongates, the neural plate broadens and extends to the oropharyngeal membrane in the cranial part of the embryo. On approximately day 18, the neural plate invaginates along its central axis to form the neural groove. By the end of the third week, the lateral edges of the neural plate becomes elevated to form neural folds. Formation of the neural crest: Masses of cells detach themselves from the lateral side of the neural plate and form the neural crest. By the end of the third week, the neural folds will begin to fuse, converting the neural plate into the neural tube. The fusion of the neural folds start in the middle of the embryo, and then the neural plate will keep fusing towards the head and tail of the embryo. The neural tube soon separates from the surface ectoderm, surface ectoderm fuses and differentiates into the epidermis of the skin. Neurulation is completed during the fourth week, Video on neurulation: https://www.youtube.com/watch?v=qzib8bdtK74 Until the fusion is complete, the cranial and caudal ends of the neural tube communicates with the amniotic cavity by the way of anterior and posterior neuropores. Closure of the cranial neuropore occurs at approx 25 days, whilst the posterior neuropore closes at day 28. Upon closure of the caudal neuropore, the embryo has established a rudimentary spinal cord caudally and the brain vesicles cranially. to have learn appreciate i