Changes

== Neuralation ==

== Neuralation ==

=== Primary Neuralation ===

=== Primary Neurulation ===

Cells of the neural plate proliferate, causing the neural plate to thicken. Cells then converge at the midline and become wedge shaped, which drives the neural plate to become long and narrow. Cells along the midline descend ventrally and contact the notochord, forming a "hinge". This forms a depression which is called the '''neural groove'''. Either side of the neural groove, ectoderm converges towards the midline. This causes elevations either side of the neural groove, called '''neural folds'''. Hinges form at the foot of each neural fold, allowing the folds to be brought together, forming a tube. The tube sinks, as non - neural ectoderm fuses above the neural tube, "zipping" the neural tube up. The non - neural ectoderm will form epidermis. Failure of the neural tube to close causes '''spina bifida''' (spinal cord protrusion) and '''exencephaly''' (brain located out of the skull).  

Cells of the neural plate proliferate, causing the neural plate to thicken. Cells then converge at the midline and become wedge shaped, which drives the neural plate to become long and narrow. Cells along the midline descend ventrally and contact the notochord, forming a "hinge". This forms a depression which is called the '''neural groove'''. Either side of the neural groove, ectoderm converges towards the midline. This causes elevations either side of the neural groove, called '''neural folds'''. Hinges form at the foot of each neural fold, allowing the folds to be brought together, forming a tube. The tube sinks, as non - neural ectoderm fuses above the neural tube, "zipping" the neural tube up. The non - neural ectoderm will form epidermis. Failure of the neural tube to close causes '''spina bifida''' (spinal cord protrusion) and '''exencephaly''' (brain located out of the skull).

=== Secondary Neurulation ===

=== Secondary Neurulation ===