Yolk sac

Yolk sac
Yolk sac
	Human embryo of 3.6 mm
	Human embryo from thirty-one to thirty-four days
Details
Carnegie stage	5b
Days	9
Precursor	Endoderm
Identifiers
Latin	vesicula umbilicalis; saccus vitellinus
MeSH	D015017
TE	sac_by_E5.7.1.0.0.0.4 E5.7.1.0.0.0.4
FMA	87180
	Anatomical terminology

The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though yolk sac is far more widely used. In humans, the yolk sac is important in early embryonic blood supply,^[1] and much of it is incorporated into the primordial gut during the fourth week of embryonic development.^[2]

^ Lutfey, Karen; Freese, Jeremy (2005). "Toward Some Fundamentals of Fundamental Causality: Socioeconomic Status and Health in the Routine Clinic Visit for Diabetes". American Journal of Sociology. 110 (5): 1326–1372. doi:10.1086/428914. ISSN 0002-9602. JSTOR 10.1086/428914. S2CID 17629087.
^ The Developing Human: Clinically Oriented Anatomy: Chapter 7

[:0-1] Lutfey, Karen; Freese, Jeremy (2005). "Toward Some Fundamentals of Fundamental Causality: Socioeconomic Status and Health in the Routine Clinic Visit for Diabetes". American Journal of Sociology. 110 (5): 1326–1372. doi:10.1086/428914. ISSN 0002-9602. JSTOR 10.1086/428914. S2CID 17629087.

[2] The Developing Human: Clinically Oriented Anatomy: Chapter 7

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