Blood islands are structures in the developing embryo which lead to many different parts of the circulatory system. They primarily derive from plexuses formed from angioblasts. Within them, vacuoles appear through liquefaction of the central part of the syncytium into plasma. The lumen of the blood vessels thus formed is probably intracellular. The flattened cells at the periphery form the endothelium. The nucleated red blood corpuscles develop either from small masses of the original angioblast left attached to the inner wall of the lumen or directly from the flat endothelial cells. In either case the syncytial mass thus formed projects from and is attached to the wall of the vessel. Such a mass is known as a blood island and hemoglobin gradually accumulates within it. Later the cells on the surface round up, giving the mass a mulberry-like appearance. Then the red blood cells break loose and are carried away in the plasma. Such free blood cells continue to divide. Blood islands have been seen in the area vasculosa in the omphalomesenteric vein and arteries, and in the dorsal aorta[WP, unvetted]. [ ]

Synonyms: blood islands

This is just here as a test because I lose it

Term information

database cross reference

uberon_slim, efo_slim, pheno_slim, vertebrate_core

plural term
blood islands

axiom lost from external ontology

relationship loss: part_of intermediate cell mass of mesoderm (TAO:0000033)[TAO]

external definition

Nests of developing blood cells arising late in the segmentation period from the intermediate mass, and located in the anterior-ventral tail, just posterior to the yolk extension. Kimmel et al, 1995.[TAO]

Region located on the ventral surface of the developing embryo that is a site of hematopoiesis and that is analogous to the yolk sac blood islands of higher vertebrates.[AAO]

external ontology notes

EHDAA2 distinguishes 3 types, but does not have a superclass. The VHOG class may refer to yolk sac

has broad synonym

ventral lateral plate mesoderm

has related synonym

posterior blood island

caudal hematopoietic tissue

posterior ICM

ventral blood island


homology notes

Small clusters of mesodermal cells called blood islands mark the embryonic debut of the cardiovascular system (in vertebrates) (reference 1); In birds and mammals, primitive hemangioblasts are extraembryonic, populating the yolk sac as the so-called blood islands (reference 2).[well established][VHOG]