Transcript of "Cardiac development & fetal circulation (2)"
CARDIAC DEVELOPMENT & FETAL
18 DAYS -
vasculogenesis .. Cell
clusters on either side of
22 days – fuse –primitive
HEART STARTS TO
22-24 days to 28 ndays
Heart bends ventrally and
Outside appearance similar to
Ostium primum , ostium secundum
S.P + O.S = foramen ovale
the dorsal aortae develop at the same time as the early heart tubes. These connect to the heart
tubes prior to fusion via the first aortic arch arteries. Other arches develop, which go on to form
the arteries of the head and neck. We also previously saw the way in which the aorta and
pulmonary trunk form. The dorsal aorta gives off branches which supply blood to the rest of the
Gut (ventral/front) branches
Lateral (side) branches
As the embryo progresses to a fetus the vasculature is still remarkably different to that of the
adult, including the presence of three vascular shunts:
foramen ovale (seen previously) - blood travels from the right atrium to the left atrium
ductus venosus - blood from the umbilical vein bypasses the liver to enter the inferior vena
ductus arteriosus - blood passes from the pulmonary trunk into the aorta
These shunts allow blood to bypass the lungs, liver and kidneys, whose functions are
performed by the placenta while in utero.
The following diagram shows the movement of blood throughout the fetal circulation. The main
flow of blood is as follows:
Placenta → umbilical vein → ductus venosus → inferior vena cava → right atrium → foramen
ovale → left atrium → left ventricle → aorta → hypogastric arteries → umbilical arteries →
placenta. Blood that passes from the right atrium to the right ventricle travels:
Right ventricle → pulmonary trunk → ductus arteriosus → aorta
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