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LifeMap Discovery

Watch the introductory video to learn more about our database of embryonic development for stem cell research and regenerative medicine

All Anatomical Compartments > Compartment Card
Extraembryonic Mesoderm >

Extraembryonic Blood Islands

Blood islands are cell aggregates in the early embryo, which first appear in the human yolk sac at approximately day 13-15 of gestation. Blood islands give rise to vascular endothelia and blood cells. The blood islands is comprised of a loose inner mass of embryonic hematopoietic precursor cells and an outer luminal layer of angioblasts.

The formation of blood islands in the yolk sac is a critical step in amniotic development.
Extraembryonic Blood Islands
Multiple Ancestors Single Ancestor No Descendants Develops from Part of Parent