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Fig. 459. Human embryo of about fourteen days, with yolk-sac

(After His.)

The anterior wall of the umbilical orifice are now continuous with the posterior ends of the anterior ventral aorta. With the formation of the tail-fold the posterior parts of the primitive aortse are carried forward in a ventral direction to form the posterior ventral aortae and primary caudal arches. In the pericardial region the two primitive aortse grow together, and fuse to form a single tubular heart (Fig. 460), the posterior end of which receives the two vitelline veins, while from its anterior end the two anterior ventral aortse emerge. The first cephalic arches pass through the mandibular arches, and behind them five additional pairs subsequently develop, so that altogether six pairs of aortic arches are formed; the fifth arches are very transitory vessels connecting the ventral aortse with the dorsal ends of the sixth arches. By the rhythmical contraction of the tubular heart the blood is forced through the aortse and bloodvessels of the vascular area, from which it is returned to the heart by the vitelline veins. This constitutes the vitelline circulation (Fig. 459), and by means of it nutriment is absorbed from the yolk (vitellus.)



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Reference

Gray H. Anatomy of the human body. (1918) Philadelphia: Lea & Febiger.


Cite this page: Hill, M.A. (2024, May 23) Embryology Gray0459.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Gray0459.jpg

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current18:07, 23 August 2014Thumbnail for version as of 18:07, 23 August 20141,195 × 961 (258 KB)Z8600021 (talk | contribs)
18:02, 23 August 2014Thumbnail for version as of 18:02, 23 August 20141,224 × 1,000 (269 KB)Z8600021 (talk | contribs)==Fig. 459. == {{Gray Anatomy}} Category:Historic Embryology Category:Gray's 1918 Anatomy Category:Human Embryo Category:Heart

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