part of part_of develops from embryo 胚胎 blood island 血岛 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]. VBI blood islands caudal hematopoietic tissue posterior ICM posterior blood island ventral blood island ventral lateral plate mesoderm 后ICM 后血岛 尾部造血组织 腹侧板中胚层 腹血岛 血岛 血岛是发育中的胚胎中的结构，产生循环系统的许多不同部分。它们主要来源于成血管细胞形成的丛。在它们内部，通过将合胞体中央部分液化成血浆产生空泡。这样形成的血管腔可能是细胞内的。外周的扁平细胞形成内皮。有核红血球体由附着在腔内壁原始的血管母细胞的小块肿块发展而来，或者直接从平坦的内皮细胞发展而来。在任何一种情况下，由此形成的合体块体从血管突出并附着在血管上。这样的肿块被称为血岛，血红蛋白在其内部逐渐积累。之后，表面上的细胞聚集起来，形成了桑葚状的外形。然后红细胞散开，在血浆中被带走。这种游离血细胞不断分裂。已经在大面积静脉和动脉的血管以及背主动脉中看见血岛，[WP，unvetted]。 lateral plate mesoderm 侧板中胚层 presumptive structure 推定结构