Growth Of The Human Embryonic Brain During Rapid Brain Growth: Area Analysis And Comparison With The Chick

The growth of the human brain during embryonic rapid brain growth: area analysis and comparison with the chick This report focuses on growth of the brain of the early human embryo, Carnegie stages 12 – 23. Areas of median sections from 52–58 embryos were measured in order to determine the best mathematical model to describe growth of the three primary brain vesicles, to determine the change in the ratio of tissue and cavity amounts (T/C) and to compare the patterns of growth of the human embryo with the chick embryo. An exponential model best describes growth of the brain and head during this time period. The head expands nearly 250-fold compared to a 171-fold growth of the brain. The whole brain, forebrain, midbrain, and hindbrain all exhibit larger cavities initially followed by a reversal of such at a critical time (stages 21 – 24 except for the presumptive cerebellum). Boxplots of the T/C ratios for the head and brain plus its components reveal that initially the tissue is less than the cavity (10–20% or 40%–50%) but eventually becomes larger (60% to 200%). A comparison of the ratios of the mean area of human brain components with the estimated area of chick brain components for selected analogous stages shows that these components all grow faster (1.37 to 1.45 times) for the human embryo than for the corresponding parts of the chick embryo. (Supported by the NIH:NINDS24136 and NICHHD:24710)