G7
An overview of blood flow through the embryo of
oxygenated blood. Note the umbilical artery and
veins anastomose within the chorion of the
placenta, there is no direct connection of maternal
and fetal blood.
Maternal Blood
umbilical vein
liver
anastomosis
ductus venosus
sinus venosus
atria ventricles
truncus arteriosus
aortic sac
aortic arches
dorsal aorta
pair of umbilical arteries
Maternal Blood
Note the position of the dorsal aortae, go back down the embryo from A7 to D3.
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Dorsal Aorta Fusion and Branching As the 2 dorsal aorta travel down the length of the embryo the fuse in the midline and give off branches both dorsally and ventrally. (click on image or section name to see full sections) |
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D3: Tiny dorsal branches of paired dorsal aortae. (Inferior cardinal veins lateral to aortae, also with small dorsal branches). |
D6: Dorsal aortae close together. |
D7,E1: Fusion of dorsal aortae into a midline vessel. |
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E2,E6: Dorsal branches of single dorsal aorta. |
F5: Dorsal aorta giving rise to a ventral branch (mesenteric artery), and branch to mesonephros (the developing kidney). |
F7: Dorsal aorta sending branch into mesonephros (to glomerulus). |
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G2,G3: Dorsal aorta curving around flexed trunk of embryo. Note spinal cord cut twice.
G4,G5: Sections gradually passing dorsally beyond curvature of single dorsal aorta.
G5 We are now below the curvature of the dorsal aorta (note the notocord cut in longitudinal section)
Follow the aorta in the lumbar region of the embryo as it passes into the sacral region.
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G2,G1: Single dorsal aorta ventral to sacral (smaller) spinal cord. |
F7-E7: Note that at the sacral end of the embryo, we are travelling downward as we move up through the sections.
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Lateral major branch of dorsal aorta becomes umbilical artery
E6,E5: it reaches a crest in E5 (i.e. not seen in E4) and then "descends" in the ventral body wall to F2, where it enters the body stalk. We will follow this complex twisting again when we study the development of the hindgut.
Next page for embryonic blood flow: embryo's venous blood
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Enjoyed this site? Visit the New 2010 Site!
In human embryos the heart begins to beat at about 22-23 days, with blood flow beginning in the 4th week.
The heart is therefore one of the earliest differentiating and functioning organs. (More? see recent review article). Most texts will separate heart development from vascular development in order to simplify their descriptions of cardiovascular development, though the 2 are functionally and embryologically connected.
The heart develops from cardiogenic mesoderm that originally lies above the cranial end of the developing neural tube. Enlargement of the cranial neural fold brings this region ventrally to its correct anatomical position. The original paired cardiac tubes fuse, with the "ventricular" primordia initially lying above the "atria". Growth of the cardiac tube flexes it into an "S-shape" tube, rotating the "ventricles" downward and pushing the "atria" upward. This is then followed by septation, a complex process which converts this simple tube into a four chambered heart. A key part of this process is the separation of cardiac outflow (truncus arteriosus) into a separate pulmonary and aortic arch outflow. During embryonic development there is extensive remodelling of the initially r/l symetrical cardiovascular system and a contribution from the neural crest to some vessels.
Please email Dr Mark Hill if you wish to make a comment about this current project.
