human Archives - 3DBiology.com

In this 3D animation we go over the development of the human brain cortex, including formation and differentiation of nerve cells from precursor cells, migration of immature nerve cells to their eventual positions, growth of axons building a network and formation of synapses. Review: For the human brain to function a long process of developmental events must take place. In four weeks the fertilized egg has turned into billions of cells which will form the nervous muscular, vascular, digestive and skeletal systems of the human body. Within the first month the bulbous head and the arching back of the four millimeter long embryo are clearly visible. The structures which will give rise to the brain and spinal cord are now the most developed parts of the embryo. The brain will form from the cerebral vesicle. The wall of the cerebral vesicle is built of columnar neural epithelium. Divisions of these neural epithelial cells will produce neuroprogenitor cells. They will generate neurons and glial cells of the brain cortex. In a mitotic division the genetic material is doubled and distributed among two daughter cells. The process is repeated resulting in growth of the diameter of the cerebral vesicle. At 30 to 40 days some of the non-dividing cells produce processes and form a marginal zone. Glial cells form a scaffold for neurons to migrate on and eventually form the cortical plate. The cortical plate will become the cerebral cortex whereas the intermediate zone will transform into white matter. Neurons that have reached the cortical plate grow and differentiate into granular and pyramidal cells and form the five layers of the cerebral cortex. Granular and pyramidal cells form cortical minicolumns. Neurons of a minicolumn make excitatory and inhibitory connections both within each column as well as between many columns. Mini columns are an elementary unit of the cortical network involved in signal generation and transmission. In a four-month-old fetus the brain context contains all major anatomical and functional subdivisions including visual, auditory, speech and motor. Click here for an animation on human brain anatomy as well as physiology.