The marked structure close at which day of in-utero development (JIPMER May 2019)
High-Yield Explanation
- The picture is showing dorsal surface of fetus, having neural tube - have 2 openings anterior neuropore (cranially) - forms brain; posterior neuropore (caudally) - forms spinal cord - On dorsal surface of fetus- Notochord (axial mesoderm) stimulate overlying ectoderm to form | Neural plate ectoderm which becomes | Neural groove | Detaches from dorsal surface, fuses at cervical region & proceed Caudally & cranially forming neural tube Surface ectoderm in periphery come to midline & fuse together forming skin epithelium covering neural tissue Neural Crest Cells at periphery detach from dorsal surface to from Peripheral nervous system - Neural tube - will have 2 opening, which closes during course of development - Non closure leads to Open Neural Tube Defects. 1. Towards head - Cranial/anterior neuropore - closes & form brain by days Non closure of anterior neuropore leads to Anencephaly | Leading to open brain & skull cap Small degenerated brain is present.These fetus doesn't have swallow reflex resulting in polyhydramnios (more Amniotic Fluid) 2. Towards tail - Caudal/Posterior neuropore - closes & form spinal cord by day-28 Non-closure of posterior neuropore leads to Rachischisis Spinal cord & veebra are open (open veebra - spinal bifida) Skin is also open & CSF keep leaking outside Lady with fetus of open neural tube defects will have increased levels of ALPHA FETO-PROTEIN & ACETYLCHOLINESTARASE enzyme Mother with polyhydramnios - check for AFP - If high check for AchE - if high do USG | It may be a case of Anencephaly / Rachischisis - Open neural tube defects can be prevented by giving prophylactic Folic acid supplements Dose - 400ug/day - Antenatal as well as postnatal throughout the pregnancy - Both anencephaly & rachischisis come together forming craniorachischisis. Skin remains at periphery; veebra are open & veebra spines are not fused resulting in spina bifida Spinal cord is open & CSF is leaking out. A - Craniorachischisis B - Anencephaly