File:Patten048.jpg

Fig. 48. Diagram to show course of vitelline circulation in chick of about four days

(After Lillie.)

For the intra-embryonic vessels see Fig. 47. The direction of blood flow is indicated by arrows.

Abbreviations:

• A, dorsal aorta
• A.V.V., anterior vitelline vein
• L.V.V., lateral vitelline vein
• M.V., marginal vein (sinus terminalis)
• P.V.V., posterior vitelline vein
• V.A., vitelline artery.

The course of the vitelline circulation in chicks of four days is shown diagrammatically in Figures 47 and 48. Circulating in the rich plexus of small vessels on the yolk, the blood finally makes its way either directly into one or another of the larger vitelline veins, or to the sinus terminalis which acts as a collecting channel, and then over the sinus terminalis to one of the vitelline veins. The vitelline veins conVerge toward the yolk-stalk where they empty into the omphalomesenteric veins. The omphalomesenteric veins at first paired throughout their entire length have been brought together proximally by the closure of the ventral body wall and become fused to form a median vessel within the body of the embryo. It is through this vessel that the vitelline blood eventually reaches the heart. In the heart the blood of the vitelline, intra-embryonic, and allantoic circulations is mingled. The mixed blood passes out by the ventral aorta and the aortic arches into the dorsal aorta. Leaving the dorsal aorta through the vitelline arteries the blood is returned to the yolk-sac.

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Reference

Patten BM. The Early Embryology of the Chick. (1920) Philadelphia: P. Blakiston's Son and Co.

Cite this page: Hill, M.A. (2024, April 25) Embryology Patten048.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Patten048.jpg

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