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By the beginning of the 4th week of human development, a ventral view illustrates several important structures:

the anterior-most aspect of the brain (forebrain, prosencephalon),

the heart (which is just beginning to beat),

the foregut region dorsal to the heart,

and the developing hindgut.

                     Species: Mouse 
                     Day Gestation: 8 
             Approx. Human Age: 22 Days 
                                   View: Ventral 
                  Neurulation
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