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an aggregation of splanchnic mesodermal cells on the embryonic yolk sac, with the potentiality of forming vascular endothelium and primordial blood cells.
Synonym(s): blood islet
one of the clusters of mesodermal cells that proliferate on the outer surface of the embryonic yolk sac and give it a lumpy appearance.
The early collections of cells in the embryo that give rise to blood and blood-forming organs later in life.
See also: island