Development and Evolution of Nervous Systems 2

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The nervous system and skin come from the ectoderm layer of the embryo with the neual groove developing after 17 days.

The walls of the groove are known as folds which fuse dorsally to form the neural tube.

The CNS develops from the neural tube.The rostral end of the neural tube has 3 swellings which differentiate into the prosencephalon (forebrain), mesencephalon (midbrain) and the rhombencephalon (hindbrain). The hind brain connects with the caudal neural tube to form the spinal cord.

Vesicles sprout from the diencephalon of the forebrain, developing into the optic and telencephalic vesicles.

The optic vesicles grow and fold in, forming the optic stalks and cups which will become the optic nerves and retinas.

The telencephalic vesicles form the telencephalon which has two hemispheres, developing posteriorly so that they lie over and laterally to the diencephalon.There is another pair of vesicles that sprout and form the olfactory bulbs. 

White matter systems develop and the cells in the telencephalon walls divide and differentiate into various structures. The axons from the neurons of the developing forebrain form the cortical white matter, corpus callosum and the internal capsule. The corpus callosum forms an axonal bridge linking the cerevral hemispheres. The cerebral cortex and the basal telencephalon develop from the neurons in the telencephalic vesicles.

The thalamus and hypothalamus develop from the diencephalon.

As the neural tube forms, part of the ectoderm gets pinched off to form the neural crest. This is where the peripheral nerves will originate from.

Neurulation is the process of the neural…


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