Vitelline circulation

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Human embryo of 2.6 mm.

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Diagram of the vascular channels in a human embryo of the second week. (After Eternod.) The red lines are the dorsal aortæ continued into the umbilical arteries. The red dotted lines are the ventral aortæ, and the blue dotted lines the vitelline veins.

Vitelline circulation refers to the system of blood flowing from the embryo to the yolk sac and back again.

The yolk-sac is situated on the ventral aspect of the embryo; it is lined by entoderm, outside of which is a layer of mesoderm. It is filled with fluid, the vitelline fluid, which possibly may be utilized for the nourishment of the embryo during the earlier stages of its existence. Blood is conveyed to the wall of the sac by the primitive aortæ, and after circulating through a wide-meshed capillary plexus, is returned by the vitelline veins to the tubular heart of the embryo. This constitutes the vitelline circulation, and by means of it nutritive material is absorbed from the yolk-sac and conveyed to the embryo.

External links

• Gray's page #54
• Overview of three circulation systems

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.