forumdoctor
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Blood from the placenta is about 80% oxygenated. However, mixture with unoxygenated blood at various points reduces the oxygen content. Which of the following vessels contains blood with the highest oxygen content?
A.
Abdominal aorta
B.
Common carotid arteries
C.
Ductus arteriosus
D.
Pulmonary artery
E.
Pulmonary vein
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| me007
Forum Guru
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d
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| indidoc1
Forum Guru
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B.
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| peggy
Forum Newbie
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B
because from the umbilical vein it goes to ductus venosus which comes together with inferior vena cava, which enters RA, the blood then goes through foramen ovale to LA, LV and into ascending aorta (65% oxygenated) which gives carotids an blood supply to head and neck.
the blood form superior VC (40% oxygentaed) enters RA, RV and goes to pulmonary artery, and through ductus arteriosus into descending aorta (60 % oxygenated). you can already exclude these two answers because I think the O2 concentration in DA and in PA is the exactly the same.
GL
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| forumdoctor
Forum Senior
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Friends, really fast response, peggy good explanation, i was also thinking of D.
gl
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| new_n_lost
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| epica
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Discussion
The fetal circulation is significantly different from that of the adult because the fetus gets oxygen from its mother, via the placenta, instead of through the lungs (i.e., the placenta provides respiratory function). Three primary shunts are designed to get the most oxygenated blood to the developing tissues: the ductus venosus, foramen ovale, and ductus arteriosus.
Anatomy
In utero, oxygen is released from maternal RBCs and picked up by fetal RBCs, which contain large amounts of fetal hemoglobin (e.g., hemoglobin F) and have an oxygen dissociation curve that is shifted up and to the left (i.e., greater oxygen affinity). This occurs in the left umbilical vein, the location of the blood with the highest oxygen saturation. Blood flows through the umbilical vein up to the liver, where most of it is shunted through the ductus venosus, bypassing the liver, to enter the inferior vena cava. From the inferior vena cava, blood flows into the right atrium, mixing with deoxygenated blood returning to the heart from the superior vena cava. Then the blood is largely shunted across the foramen ovale and into the left atrium, left ventricle, aorta, and systemic arteries to supply oxygen and nutrients to the developing organs.
When blood flows through the capillaries and returns to the heart by systemic veins, it goes into the right atrium and right ventricle and out into the main pulmonary artery. The pulmonary artery pressures are high because the lungs are not inflated, however, and most blood is preferentially shunted through the ductus arteriosus into the descending thoracic aorta. Blood returns to the placenta via the aorta and iliac arteries, then through the umbilical arteries to reach the placenta.
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