VIBS 305 Lecture 13: Fetal Circulation
17 Mar 2018
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Peculiarities of fetus: lungs are nonfunctional, lungs present resistance to blood flow, o2 and co2 and nutrient/waste exchange take place in placenta. Changes that occur at birth: neonate no longer sends blood through the placenta, doubles the systemic vascular resistance, animal takes first breath and lungs inflate. Increased aortic, left atrial and left ventricular pressures: pulmonary vessels no longer physically compressed oxygen in lungs leads to vasodilation of pulmonary arteries, decreased pulmonary arterial pressure, right atrial and. Increased pulmonary blood flow right ventricular pressures: fetal structures, change in pressure, foramen ovale, changes in relative pressures between the right and left atria results in functional closure of the foramen ovale. In the fetus, pressure on right is greater than pressure on left (keeps it open) Ductus arteriosus lumen begins to seal with fibrous tissue. Increase in oxygen tension: ductus arteriosus, umbilical arteries and veins, unknown 9possibly oxygen tension, ductus venosus.
