In the embryonic stage, the brain begins to undergo rapid development, which causes the head to represent about 50 percent of the total length of the embryo.
This is regarded as an early stage of development in multicellular organisms and is characterized by an organism which is undergoing development in the egg or uterus of the females.
The brain which is a vital organ and components of the central nervous system develops rapidly so as to enable coordination of different activities. This is therefore the reason why it is necessary for it to fully develop first before other parts as it also contains rich network of neurons necessary for its reaction to different types of stimuli.
In this stage, the brain represents about fifty percent of the total length of the embryo when observed.
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