Yolk sac
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, and much of it is incorporated into the primordial gut during the fourth week of embryonic development.
| 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 | |
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