yolk sac


Definition of yolk sac

: a membranous sac of most vertebrates that encloses the yolk, is attached in most forms (as in humans) through the yolk stalk with the intestinal cavity of the embryo, and is supplied with blood vessels that transport nutritive yolk products to the developing embryo

Examples of yolk sac in a Sentence

Recent Examples on the Web By day 8, a beating heart began to circulate blood through vessels forming around the embryo’s yolk sac. Megan Molteni, STAT, 2 Aug. 2022 McKenna Shea Xydias, of Senoia, Georgia, had an ovarian yolk sac tumor, according to Good Morning America, and went through four rounds of chemotherapy. Caitlin Keating, PEOPLE.com, 20 June 2019 But in the human embryo knockouts, placental cells and yolk sac cells also failed to form. Gretchen Vogel, Science | AAAS, 20 Sep. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'yolk sac.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of yolk sac

1831, in the meaning defined above

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The first known use of yolk sac was in 1831

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Dictionary Entries Near yolk sac

yolk plate

yolk sac

yolk-sac placenta

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Last Updated

8 Aug 2022

Cite this Entry

“Yolk sac.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/yolk%20sac. Accessed 15 Aug. 2022.

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More Definitions for yolk sac

yolk sac


Medical Definition of yolk sac

: a membranous sac of most vertebrates that is attached to an embryo and encloses the yolk, that is continuous in most forms including humans through the omphalomesenteric duct with the intestinal cavity of the embryo, that is abundantly supplied with blood vessels which transport nutritive yolk products to the developing embryo, and that in placental mammals is nearly vestigial and functions chiefly prior to the formation of the placenta

More from Merriam-Webster on yolk sac

Britannica English: Translation of yolk sac for Arabic Speakers

Britannica.com: Encyclopedia article about yolk sac


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