Anatomy

Yolk Sac

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.

National Library of MedicineMedical Subject Headings2026

Structured Summary

Abstract

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.

MeSH Record

Classification

Broader headings

Related Concepts

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MeSH Record

Synonyms

6 entry terms
  • Vitelline Sac of Embryo
  • Embryo Vitelline Sac
  • Embryo Vitelline Sacs
  • Sac, Yolk
  • Sacs, Yolk
  • Yolk Sacs

MeSH Record

Aspects Covered

24 allowable subheadings

Indexed with the subheadings abnormalities, anatomy & histology, blood supply, chemistry, cytology, diagnostic imaging, drug effects, embryology, enzymology, growth & development, immunology, injuries, innervation, metabolism, microbiology, parasitology, pathology, physiology, physiopathology, radiation effects, surgery, transplantation, ultrastructure, virology.

MeSH Record

History Note

78; was see VITELLINE MEMBRANE 1973-77

MeSH Record

Previous Indexing

  • Chick Embryo (1966-1972)
  • Fetal Membranes (1966-1972)
  • Vitelline Membrane (1966-1974)

MeSH Hierarchy

Tree Numbers

  1. A10w.615w.284w.981w
  2. A16.254.750w.981w
  3. A16.331.800w

AMA Style

References

  1. National Library of Medicine. Yolk Sac. Medical Subject Headings (MeSH). 2026. Unique ID D015017. http://id.nlm.nih.gov/mesh/2026/D015017
  2. Yolk Sac. In: Wikipedia. https://en.wikipedia.org/wiki/Yolk_sac
  3. Yolk Sac. In: Wikidata. https://www.wikidata.org/wiki/Q369887