Formation of Heart Loop
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Questions and Answers

What is the correct order of heart development?

  • Heart tube → atrium, ventricle, bulbus cordis, truncus arteriosus, conus cordis, sinus venosus
  • Heart tube → atrium, bulbus cordis, ventricle, truncus arteriosus, conus cordis, sinus venosus
  • Heart tube → ventricle, atrium, bulbus cordis, truncus arteriosus, conus cordis, sinus venosus
  • Heart tube → bulbus cordis, ventricle, atrium, truncus arteriosus, conus cordis, sinus venosus (correct)
  • What happens to the heart tube as it grows?

  • It remains straight and grows outside the pericardial cavity
  • It becomes twisted and forms a knot
  • It undergoes bending and cannot be accommodated within the pericardial cavity (correct)
  • It becomes smaller and accommodates within the pericardial cavity
  • What is the function of the sinus venosus?

  • It connects the atrium to the ventricle
  • It pumps blood from the ventricle to the atrium
  • It is a part of the bulbus cordis
  • It receives veins from the body (correct)
  • What is the relationship between the bulboventricular loop and the cephalic portion?

    <p>The cephalic portion bends ventrally, caudally, and slightly to the right to form the bulboventricular loop</p> Signup and view all the answers

    What happens to the atrium during heart development?

    <p>It moves dorsocranially and bulges laterally on each side of the bulbus</p> Signup and view all the answers

    What is the fate of the proximal part of the bulbus?

    <p>It develops into the primitive right ventricle</p> Signup and view all the answers

    What are the two terms used somewhat confusingly for the parts at the arterial end?

    <p>Truncus arteriosus and conus arteriosus</p> Signup and view all the answers

    What is the connection between the truncus arteriosus and the conus arteriosus?

    <p>The truncus arteriosus leads to the conus arteriosus</p> Signup and view all the answers

    Which blood vessel carries oxygen-rich blood to the fetus?

    <p>Umbilical vein</p> Signup and view all the answers

    What structure directs most of the blood from the IVC into the left atrium?

    <p>Crista dividens</p> Signup and view all the answers

    What is the primary function of the fetal lungs?

    <p>Production of surfactant</p> Signup and view all the answers

    Which part of the heart receives blood from the superior vena cava (SVC)?

    <p>Right atrium</p> Signup and view all the answers

    What happens to the blood that does not pass through the foramen ovale in the fetal heart?

    <p>It mixes with blood from the SVC and coronary sinus in the right ventricle</p> Signup and view all the answers

    What is the oxygen content of the blood that leaves the right ventricle through the pulmonary trunk?

    <p>Medium oxygen content</p> Signup and view all the answers

    What is the main difference between the blood in the IVC and the blood in the umbilical vein?

    <p>The IVC carries oxygen-poor blood, while the umbilical vein carries oxygen-rich blood.</p> Signup and view all the answers

    What is the primary effect of Tetralogy of Fallot?

    <p>Cyanosis</p> Signup and view all the answers

    Which of the following receives well-oxygenated blood from the umbilical vein?

    <p>The liver</p> Signup and view all the answers

    Which of the following is a characteristic of Persistent Truncus Arteriosus?

    <p>Truncus overrides both ventricles</p> Signup and view all the answers

    What is the origin of the aorta in Transposition of Great Vessels?

    <p>Right ventricle</p> Signup and view all the answers

    What is the resulting effect of Tetralogy of Fallot on pulmonary flow?

    <p>Decreased pulmonary flow</p> Signup and view all the answers

    What is the characteristic of cyanotic heart defects?

    <p>Decreased oxygenation</p> Signup and view all the answers

    What is the percentage of all CHDs that Tetralogy of Fallot accounts for?

    <p>5-7%</p> Signup and view all the answers

    What is the defect accompanied by in Persistent Truncus Arteriosus?

    <p>Ventricular septal defect</p> Signup and view all the answers

    What is the characteristic of Transposition of Great Vessels?

    <p>Aorta originates from right ventricle</p> Signup and view all the answers

    What is the primary reason for the thinning of the pulmonary artery walls during the first few breaths?

    <p>Stretching of the arteries due to lung expansion.</p> Signup and view all the answers

    What causes the pressure in the left atrium to be higher than in the right atrium after birth?

    <p>Increased pulmonary blood flow and decreased umbilical vein flow.</p> Signup and view all the answers

    What is the main reason for the reversal of blood flow in the ductus arteriosus (DA) after birth?

    <p>Lower pulmonary vascular resistance compared to systemic vascular resistance.</p> Signup and view all the answers

    How does the increased workload of the left ventricle after birth affect the ventricular walls?

    <p>The left ventricular wall becomes thicker due to increased workload.</p> Signup and view all the answers

    What is the usual timeframe for the functional closure of the ductus arteriosus in a normal full-term infant?

    <p>Within 24 to 48 hours of birth.</p> Signup and view all the answers

    Which of the following conditions can cause the ductus arteriosus to remain open longer?

    <p>Premature birth.</p> Signup and view all the answers

    What is the primary function of the ductus arteriosus in a fetus?

    <p>To bypass the lungs and deliver oxygenated blood directly to the systemic circulation.</p> Signup and view all the answers

    Which of these structures is NOT directly involved in the transition of fetal circulation to neonatal circulation?

    <p>Aorta.</p> Signup and view all the answers

    What is the primary function of the ductus venosus in fetal circulation?

    <p>To connect the umbilical vein to the inferior vena cava</p> Signup and view all the answers

    Which vascular structures are critical during the transitional circulation at birth?

    <p>Foramen ovale, ductus venosus, and ductus arteriosus</p> Signup and view all the answers

    What happens to blood flow in the ductus venosus when the sphincter contracts?

    <p>More blood is diverted to the portal vein and hepatic sinusoids</p> Signup and view all the answers

    What characterizes the state of pulmonary vessels prenatally?

    <p>They are constricted, inhibiting gas exchange</p> Signup and view all the answers

    What is the effect of uterine contractions on blood flow in the umbilical vein?

    <p>They can lead to heart overload by increasing venous flow</p> Signup and view all the answers

    How does typical blood flow from the placenta reach the heart in fetal circulation?

    <p>Through the umbilical vein and ductus venosus to the inferior vena cava</p> Signup and view all the answers

    What type of blood is primarily delivered to the fetus from the placenta?

    <p>Oxygen-rich, nutrient-rich blood</p> Signup and view all the answers

    What is the role of the foramen ovale in fetal circulation?

    <p>To shunt blood from the right atrium to the left atrium</p> Signup and view all the answers

    Study Notes

    Formation of the Heart Loop

    • Heart tube components include bulbus cordis, ventricle, atrium, truncus arteriosus, conus arteriosus, and sinus venosus.
    • As the heart tube grows, it bends to fit within the pericardial cavity; primitive heart chambers become recognizable.
    • Sinus venosus receives blood from body veins; blood flow continues from the ventricle into the bulbus cordis and then to the arteries.

    Bending of the Heart Tube

    • Bulboventricular portion forms a loop with a cephalic portion that bends ventrally, caudally, and slightly to the right.
    • The atrium bulges laterally from the bulbus, moving dorsocranially.

    Fetal Blood Flow Dynamics

    • Fetal lungs do not provide gas exchange; key structures in transitional circulation include ductus venosus, foramen ovale, and ductus arteriosus.
    • Highly oxygenated blood from placenta enters the fetus via the umbilical vein under high pressure.

    Ductus Venosus Functionality

    • Ductus venosus connects umbilical vein to inferior vena cava (IVC), allowing half the blood to bypass the liver.
    • Blood flow through the ductus venosus is regulated by a sphincter mechanism, diverting blood based on pressure changes.

    Entry and Mixing of Blood

    • Blood in the IVC mixes poorly oxygenated blood from the lower body with well-oxygenated blood from the placenta before entering the right atrium.
    • Most blood from IVC is channeled through the crista dividens into the left atrium, mixing with smaller amounts of poorly oxygenated blood returning from lungs.

    Postnatal Circulation Changes

    • At birth, increased pulmonary blood flow leads to higher pressure in the left atrium, functionally closing the foramen ovale.
    • Blood from the right ventricle flows into the pulmonary trunk; pulmonary vascular resistance drops compared to systemic vascular resistance.

    Right and Left Ventricular Development

    • In fetuses, right ventricular wall is thicker due to increased workload; after birth, left ventricular wall becomes thicker as it takes on more responsibility.
    • Ductus arteriosus may constrict postnatally, often closing completely within 96 hours in healthy infants.

    Congenital Heart Defects

    • Tetralogy of Fallot includes pulmonary stenosis, ventricular septal defect, overriding aorta, and right ventricular hypertrophy; results in cyanosis.
    • Persistent truncus arteriosus occurs when truncoconal ridges fail to fuse, causing cyanosis and increased blood flow to the lungs.
    • Transposition of great vessels arises from abnormal descending of truncoconal septum, leading to aorta originating from right ventricle.

    Implications of Fetal Circulation

    • Fetal circulation relies on overlaying structures allowing for bypassing of lungs; post-birth adaptations are crucial for normal gas exchange transition.
    • Morphological changes and vascular resistance alterations are key factors for the heart's functional shift from prenatal to neonatal life.

    Additional Heart Defects

    • Persistence of ductus arteriosus in preterm infants; closure rates vary significantly between full-term and preterm infants.
    • Circulatory anomalies can compromise oxygenation and normal function, necessitating careful monitoring and intervention when necessary.

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    Description

    Quiz on the formation of heart loop, covering stages of heart tube development from bulbus cordis to sinus venosus.

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