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Anatomy and Cell Biology
Anatomy and Cell Biology 3319
Peter Merrifield

Anatomy NotesSept 2711 At 19 days the neural plate that is composed of dorsal ectoderm cells begins to fold in forming neural folds and a neural groove At 20 days neural fold cells migrate to form the neural crest At 22 days the neural folds close forming the neural tube which has detached from the surface ectoderm The fluid inside the neural tube later becomes the cerebral spinal fluid The neural crest cells begin to break off and form their own structure Closure of the neural tube starts at the midpoint and moves towards the cranial and caudal ends Sometimes there may not be complete closure however Anencephaly is failure of the rostral cranial part of the neural tube to close Spina bifida is failure of the caudal part of the neural tube to close At 24 days there is complete closure The rostral brain part begins to differentiate around day 24 into 3 different structures prosencephalon mesencephalon rhombencephalon From these 3 structures we get the adult brain The neural tube is composed of neuroepithelial cells These cells divide migrate externally and become neuroblasts future neurons This happens at week 5 External to the neuroepithelium the neuroblasts cluster into an alar plate and a basal plate There are four different areas around the neural tube where cells are being produced The alar and basal plates are collectively known as the mantle There is a sulcus limitans that goes through the middle of the central cavity At week 6 the neural crest cells form the sensory neurons which form dorsal root ganglia outside This is why the cell bodies of sensory neurons lie outside the CNS because they dont arise from the neural tube Dorsal neuroblasts of the alar plate become interneurons and remain in the CNS Axons extending from the interneurons form the white matter Ventral neuroblasts of the basal plate become motor neurons Their axons grow out to the effector organs Fully differentiated neurons do not divide The brain arises as the rostral part of the neural tube in week 4 of developmen
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