Fetal Circulation
From MyMCAT
Contents |
Introduction
Multiple adaptations exist in the circulatory system while in the fetal stages to better assist development.
Ductus Veinosus
Because the fetus relies on its mother for receiving nutrients and removing waste (through the placenta), the fetus has shunt which allows most blood to bypasses the liver. This is also important as the liver is not mature enough to begin processing blood.
Foramen Ovale
Because the lungs are underdeveloped and submerged in water, gas exchange (breathing) is meaningless during fetal development. To avoid this, a shunt between the right atrium and left atrium allows blood to flow straight through, without entering the pulmonary artery (and thus, lungs).
Ductus arteriosus
To further prevent blood from entering the lungs, a vessel connects the pulmonary artery to the aorta, thus allowing any blood which did not bypass the lungs through the foramen ovale, to get a second chance.
Fetal Hemoglobin
Because developing and rapidly growing tissue requires an extensive oxygen supply, fetal hemoglobin is produced instead of adult hemoglobin. This specialized hemoglobin has a high affinity for oxygen and as such, improves the effeciency at which oxygen is exchanged in the placenta. (Oxygen found in hemoglobin in the mother favours being transfered to the high affinity fetal hemoglobin.)
