Embryology of the Heart

  1. When during gestation does the heart begin to beat?
    Day 22
  2. When during gestation does heart looping occur?
    Week 4
  3. What is heart looping?
    Folding and ending of a simple heart tube
  4. The major events resulting in formation of the heart structures are occurring during which period?
    Embryonic period
  5. What is the critical period for heart development?
    Mid-week 3 – week 6
  6. What is the most common type of birth defect?
    Congenital heart defects
  7. From which germ layer does the heart arise from?
    Mesoderm, with a bit of ectoderm
  8. What is dextrocardia?
    Heart develops as it’s mirror imaging, with apex pointing to the right
  9. What causes dextrocardia?
    Disruption of the signaling pathway that determines laterality
  10. How does body folding affect the formation of the heart?
    Heart forming region is brought to a ventral position (from a cranial position)
  11. Where does the heart rank in the order of organs developed in the fetus?
    Primitive heart tube is first
  12. What is the truncus arteriosus?
    Outflow region of the primitive heart tube
  13. What structures will the truncus arteriosus become in the heart?
    • Aorta
    • Pulmonary trunk
  14. What structures will the bulbus cordis become in the heart?
    Smooth parts of both ventricles
  15. What structures will the primitive ventricle become in the heart?
    Trabeculated part of both ventricles
  16. What structures will the primitive atrium become in the heart?
    Trabeculated part of both atria
  17. What structures will the sinus venosus become in the heart?
    • Smooth part of right atrium
    • Coronary sinus
  18. What is the order of the embryonic dilations of the primitive heart tube from cranial to caudal?
    • Truncus arteriosus
    • Bulbus cordis
    • Primitive ventricle
    • Primitive atrium
    • Sinus venosus
  19. What is heart looping?
    The repositioning process happening so that future chambers are placed closer to their final positions
  20. During heart looping, what are the bending directions of the cranial portion of the heart tube?
    Bends ventrally, caudally, and to the right
  21. During heart looping, what are the bending directions of the caudal portion of the heart tube?
    Bends dorsally, cranially, and to the left
  22. What is partitioning of the heart?
    Building internal anatomy to separate the chambers
  23. What are the key events in partitioning of the heart?
    • Endocardial cushions divide AV canal
    • Atrial septation
    • Ventricular septation
    • Remodeling of the outflow tracts
  24. When in development does endocardial cushions divide the AV canal?
    Weeks 4-5
  25. When in development does atrial septation occur?
    Weeks 4-5
  26. When in development does ventricular septation occur?
    Weeks 4-5
  27. What is the atrioventricular canal?
    Junction between the future atria and future ventricles
  28. Describe the process of endocardial cushions dividing the AV canal
    Superior endocardial cushion and inferior endocardial cushion grow towards each other and divide the AV canal into a left and right AV canal
  29. What is an endocardial cushion defect?
    Atria and ventricles connected centrally
  30. What is the first wall built in the heart?
    Septum primum
  31. What is the ostium primum?
    Gap between septum primum and endocardial cushions
  32. What is the septum secundum?
    Second wall that forms and overlaps the septum primum
  33. The opening left by the septum secundum is called the ___________________
    Foramen ovale
  34. What happens to the septum primum and septum secundum?
    • Upper part of septum primum disappears and remaining part becomes valve for foramen ovale
    • Septum secundum becomes foramen ovale
  35. Describe the process of ventricular septation
    • Interventricular septum grows toward endocardial cushions
    • Interventricular foramen closed by membranous IV septum
  36. What is an atrial septal defect?
    Hole between atria does not close (heart murmur heard)
  37. In an atrial septal defect, does blood flow right to left or left to right? Why?
    • Left to right
    • Higher pressure on left side
  38. What is a ventricular septal defect? In which direction does blood usually flow?
    • Hole between atria and ventricles
    • Left to right
  39. Why is it common for people with congenital facial deformities to also have congenital heart defects?
    Neural crest cells involved in both facial development and heart development
  40. Describe remodeling of the outflow tracts
    Neural crest cells grow into ridges that twist and fuse to form aorticopulmonary septum (divides truncus arteriosus into aorta and pulmonary trunk)
  41. What is transposition of the great arteries (TGA)?
    Pulmonary aorta and aorta are switched so oxygenated blood goes to lungs and deoxygenated blood goes to body
  42. What is the treatment for TGA?
    Hole made in atrial septum to let blood mix, then surgery to switch the arteries
  43. What is tetralogy of Fallot?
    • Ventricular septal defect: hole between ventricles
    • Pulmonary stenosis: narrowing of pulmonary artery and valve
    • Overriding aorta: aorta enlarged and open to both ventricles
    • Ventricular hypertrophy: right ventricle muscular wall bigger
  44. What causes tetralogy of Fallot?
    Unequal growth of the aorticopulmonary septum
  45. In, tetralogy of Fallot, in which direction does the blood usually flow in the ventricles? Why?
    • Right to left
    • Increased resistance of blood flowing into pulmonary artery because of stenosis
  46. What kind of heart defects can cause cyanosis?
    Those that cause blood shunt from right to left side
  47. What are tet spells?
    Hypercontractile episodes leading to cyanosis in tetralogy of Fallot
  48. List and describe the three fetal shunts?
    • Ductus venosus: from umbilical vein to IVC
    • Foramen ovale: from right to left atrium
    • Ductus arteriosus: from pulmonary trunk to aorta
  49. What are the embryonic remnants of fetal circulation?
    • Ligamentum venosum: remnant of ductus venosus
    • Fossa ovalis: remnant of foramen ovale
    • Ligamentum arteriosum: remnant of ductus arteriosus
  50. What is a patent ductus arteriosus? How is it treated?
    • Ductus arteriosus does not close
    • Treated with NSAIDs to the neonate
Card Set
Embryology of the Heart