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Lab 7: Vertebrate Anatomy: Difference between revisions
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→Circulatory System Adaptations for Oxygenation in the Fetus
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While a fetus is in utero the exchange of oxygen, nutrients,and waste products occurs across the placenta. Because the digestive tract, lungs and kidneys of the fetus will not begin to function until after birth, the fetal circulation has been modified to adjust blood flow to these organs. Oxygenated blood is brought to the fetal heart through the umbilical cord via the umbilical vein, and then the inferior vena cava. <BR><BR> | While a fetus is in utero the exchange of oxygen, nutrients,and waste products occurs across the placenta. Because the digestive tract, lungs and kidneys of the fetus will not begin to function until after birth, the fetal circulation has been modified to adjust blood flow to these organs. Oxygenated blood is brought to the fetal heart through the umbilical cord via the umbilical vein, and then the inferior vena cava. <BR><BR> | ||
Follow the umbilical vein, transected earlier in the dissection, as it seems to disappear in the liver. In Figure 7.5 | Follow the umbilical vein, transected earlier in the dissection, as it seems to disappear in the liver. In Figure 7.5 notice how the umbilical vein divides into two branches before reaching the liver. One branch heads to the liver while the other (called the ductus venosis) shunts about 50% of the oxygenated blood directly to the inferior/anterior vena cava and thus to the fetal heart. The blood entering the liver is eventually directed to the vena cava through the hepatic veins. After birth the umbilical vein and umbilical arteries atrophy and the ductus venosus gradually fills with connective tissue and closes (ligamentum venosum). This is one of '''three modifications''' to the fetal circulatory system. <BR><BR> | ||
Because the lungs are not functioning in the fetus, two modifications to the circulation are found within the heart: The <u>ductus arteriosus</u> and the <u>foramen ovale</u>. We will look at these two modifications more closely when dissecting the calf heart.<BR> | Because the lungs are not functioning in the fetus, two modifications to the circulation are found within the heart: The <u>ductus arteriosus</u> and the <u>foramen ovale</u>. We will look at these two modifications more closely when dissecting the calf heart.<BR> | ||
