Embryonic Structure
yolk sac Audio
yolk sac
Subclass of:
Extraembryonic membranes; Embryo, Nonmammalian
Definitions related to yolk sac:
  • Blastocyst sac, each instance of which is some extraembryonic membranous sac that connects with the midgut of some embryo.
    Foundational Model of Anatomy
    University of Washington, 2017
  • Membranous sac on the ventral aspect of the developing embryo that acts as a primitive circulatory system as well as providing nourishment.
    NCI Thesaurus
    U.S. National Cancer Institute, 2021
  • Sometimes called vitelline sac; do not confuse with vitelline membrane of the egg; an embryonic membrane formed from endoderm and mesoderm; in reptiles and birds it incorporates the yolk into the digestive tract for nourishing the embryo; in placental mammals it is the source of most of the intestinal mucosa and the site of formation of the germ cells.
    CRISP Thesaurus
    National Institutes of Health, 2006
  • The first of four extra-embryonic membranes to form during EMBRYOGENESIS. In REPTILES and BIRDS, it arises from endoderm and mesoderm to incorporate the EGG YOLK into the DIGESTIVE TRACT for nourishing the embryo. In placental MAMMALS, its nutritional function is vestigial; however, it is the source of INTESTINAL MUCOSA; BLOOD CELLS; and GERM CELLS. It is sometimes called the vitelline sac, which should not be confused with the VITELLINE MEMBRANE of the egg.
    NLM Medical Subject Headings
    U.S. National Library of Medicine, 2021
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