In most vertebrates, the yolk sac (YS) represents the very first tissue where blood cells are detected. Therefore, it was thought for a long time that it generated all the blood cells present in the embryo. This model was challenged using different animal models, and we now know that YS hematopoietic precursors are mostly transient although their contribution to the adult system cannot be excluded. In this review, we aim at properly define the different waves of blood progenitors that are produced by the YS and address the fate of each of them. Indeed, in the last decade, many evidences have emphasized the role of the YS in the emergence of several myeloid tissue-resident adult subsets. We will focus on the development of microglia, the resident macrophages in the central nervous system, and try to untangle the recent controversy about their origin.

中文翻译：

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卵黄囊造血：它对成人造血系统有贡献吗？


在大多数脊椎动物中，卵黄囊 (YS) 是第一个检测到血细胞的组织。因此，长期以来人们认为胚胎中存在的所有血细胞都是由它产生的。该模型受到不同动物模型的挑战，我们现在知道 YS 造血前体大多是短暂的，尽管不能排除它们对成人系统的贡献。在这篇综述中，我们的目标是正确定义 YS 产生的不同血液祖细胞波，并解决每种细胞的命运。事实上，在过去的十年中，许多证据都强调了 YS 在几种骨髓组织驻留成人亚群出现中的作用。我们将重点关注小胶质细胞（中枢神经系统中常驻的巨噬细胞）的发育，并试图解开最近关于其起源的争议。