Tim Taylor is a senior writer at Innerbody Research focusing on human anatomy and physiology. Tim earned both his Bachelor of Science degree in Biology and his Master's degree in Teaching from the University of Pittsburgh.

Last updated: May 5th, 2025

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The yolk sac is established during the second week of embryonic development and although it has no nutritive value, it is essential for the growth of the embryo. The umbilical cord forms as the yolk sac shrinks and usually attaches near the center of the placenta.

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