Human Embryo 26 Day Old with Placenta
Computer Generated Image from Micro-MRI, actual size of embryo = 4.0 mm - This image provides a left-sided view of the embryo during its fourth week of development. The age is calculated from the day of fertilization. The developing spinal cord can be seen, highlighted in dark yellow. The indentations in head region are pharyngeal arches, which contribute to formation and develop of the head and neck regions. The developing heart is highlighted in red, the left atrium can be observed. Early growth of the cardiovascular system begins during the third week, when blood vessels form, and continue into the following weeks of development. The round, red structure beside the embryo is the placenta. The placenta with the umbilical cord functions as a mean for transporting nutrients, waste products, and gases between mother and embryo.