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Questions and Answers
Where does the highly oxygenated, nutrient-rich blood return from the placenta in fetal circulation?
What is the vessel that connects the umbilical vein to the caudal vena cava, bypassing the liver?
Ductus venosus
Fetal lungs replenish oxygen to the blood flowing through them.
False
The oval foramen allows most blood from the caudal vena cava to pass into the ________ atrium.
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The highly oxigenated, nutrient – rich blood returns under high pressure from the placenta in the ______ vein.
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Approx. one half of the blood passes directly into the ______ – a fetal vessel connecting the umbilical vein to the caudal vena cava.
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The other half of the blood in the umbilical vein flows into the ______ of the liver and enters the caudal vena cava via the hepatic veins.
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Blood in the caudal vena cava enters the ______ atrium.
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Most blood from the caudal vena cava is directed by the inferior border of the septum secundum (crista dividens) through the ______ foramen into the left atrium.
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The arteries of the heart, head, neck and upper limbs receive well – oxygenated blood from the ______ vein.
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The liver receives well – oxygenated blood from the ______ vein.
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Approx. 10% of the blood goes to the ______.
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Approx. 10% of blood from the ascending aorta enters the ______ aorta to supply the viscera and the caudal part of the body.
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Most of the blood in the ______ aorta passes into the umbilical arteries and it returns to the placenta for reoxygenation.
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The ______ in the ductus venosus constricts – all blood entering the liver passes through the hepatic sinusoids.
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The placental circulation occludes – that causes an immediate decrease in blood pressure in the ______ vena cava and the right atrium.
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The ______ arteries constrict at birth preventing loss of the infant’s blood.
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The umbilical vein remains patent for a considerable period and may be used for blood transfusions during ______ infancy.
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The intra-abdominal part of the umbilical vein becomes the ______ ligament of the liver.
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Remnants of the ______ arteries are the round ligament of the bladder, which extend from the urinary bladder to the umbilicus.
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The ductus venosus becomes the ______ venosum.
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Functional closure of the ______ arteriosus is completed 10 to 15 hours after birth.
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Study Notes
Fetal Circulation
- Highly oxygenated, nutrient-rich blood returns under high pressure from the placenta in the umbilical vein.
- Approximately half of the blood passes directly into the ductus venosus, bypassing the liver, and enters the caudal vena cava.
- The other half of the blood in the umbilical vein flows into the sinusoids of the liver and enters the caudal vena cava via the hepatic veins.
- Blood in the caudal vena cava enters the right atrium, and most blood is directed through the oval foramen into the left atrium.
- In the left atrium, the blood mixes with poorly oxygenated blood returning from the lungs through the pulmonary veins.
- Fetal lungs use oxygen from the blood instead of replenishing it.
Blood Distribution in Fetal Life
- The arteries of the heart, head, neck, and upper limbs receive well-oxygenated blood from the umbilical vein.
- The liver receives well-oxygenated blood from the umbilical vein.
- The small amount of well-oxygenated blood remaining in the right atrium mixes with poorly oxygenated blood from the cranial vena cava and coronary sinus and passes into the right ventricle.
- Blood with medium oxygen content leaves the right ventricle through the pulmonary trunk.
- Approximately 10% of the blood goes to the lungs, and most of the blood passes through the ductus arteriosus into the aorta to the fetal body.
Changes in Circulation at Birth
- Three essential changes occur in circulation at birth, involving circulation through the lung, liver, and placenta.
- The circulation of fetal blood through the placenta ceases.
- The infant's lungs expand and begin to function, and the oxygen-rich blood from the placenta is replaced by oxygen from the air.
- The oval foramen, ductus arteriosus, and ductus venosus close, and the umbilical vessels are no longer needed.
Derivatives of Fetal Vascular Structures
Umbilical Vein and Round Ligament of the Liver
- The intra-abdominal part of the umbilical vein becomes the round ligament of the liver.
- The umbilical vein remains patent for a considerable period and may be used for blood transfusions during early infancy.
Ductus Venosus and Ligamentum Venosum
- The ductus venosus becomes the ligamentum venosum, passing through the liver from the left branch of the portal vein to the caudal vena cava.
Umbilical Arteries and Abdominal Ligaments
- Remnants of the umbilical arteries become the round ligament of the bladder, extending from the urinary bladder to the umbilicus.
- The proximal parts of the arteries remain patent and are part of the blood supply to the bladder in the adult.
Oval Foramen and Oval Fossa
- The oval foramen closes functionally at birth, and the vestige of the foramen ovale is the fossa ovale.
Ductus Arteriosus and Ligamentum Arteriosus
- Functional closure of the ductus arteriosus is completed 10 to 15 hours after birth, and anatomical closure causes the formation of the ligamentum arteriosus.
Fetal Circulation
- Approximately 10% of blood from the ascending aorta enters the descending aorta to supply the viscera and caudal part of the body.
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- Most of the blood in the descending aorta passes into the umbilical arteries and returns to the placenta for reoxygenation.
Changes in Circulation at Birth
- Three essential changes occur in circulation at birth, involving the lung, liver, and placenta.
- The circulation of fetal blood through the placenta ceases.
- The infant's lungs expand and begin to function.
- The oval foramen, ductus arteriosus, ductus venosus, and umbilical vessels are no longer needed.
Changes in Circulation at Birth (continued)
- The sphincter in the ductus venosus constricts, and all blood entering the liver passes through the hepatic sinusoids.
- The placental circulation occludes, causing an immediate decrease in blood pressure in the caudal vena cava and the right atrium.
- Pulmonary blood flow increases.
- The pressure in the left atrium is higher than in the right atrium.
- The increased left atrial pressure closes the oval foramen by pressing the valve of the foramen against the septum secundum.
- The output from the right ventricle then flows entirely into the pulmonary circulation.
Derivatives of Fetal Vascular Structures
Umbilical Vein and Round Ligament of the Liver
- The intra-abdominal part of the umbilical vein becomes the round ligament of the liver.
- The umbilical vein remains patent for a considerable period and may be used for blood transfusions during early infancy.
Ductus Venosus and Ligamentum Venosum
- The ductus venosus becomes the ligamentum venosum.
- The ligamentum venosum passes through the liver from the left branch of the portal vein to the caudal vena cava to which it is attached.
Umbilical Arteries and Abdominal Ligaments
- Remnants of the umbilical arteries are the round ligament of the bladder, extending from the urinary bladder to the umbilicus.
- The proximal parts of the arteries remain patent and are part of the blood supply to the bladder in the adult.
- The patent part extends from the internal iliac arteries to the urinary bladder.
Oval Foramen and Oval Fossa
- The oval foramen closes functionally at birth.
- The vestige of the foramen ovale is the fossa ovale.
- The septum primum forms the floor of the oval fossa.
- The inferior edge of the septum secundum forms a rounded fold, the border of the oval fossa (limbus foraminis ovalis).
Ductus Arteriosus and Ligamentum Arteriosum
- Functional closure of the ductus arteriosus is completed 10 to 15 hours after birth.
- Anatomical closure causes the formation of the ligamentum arteriosum.
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Description
Learn about the circulation of blood in a fetus, including the path of oxygenated blood from the placenta to the heart. Understand how the ductus venosus and liver are involved in this process.
