Heart Development S1M3

  1. The heart precursor cells sit within the primary cardiogenic field which is
    A horse shoe shaped zone of splanchnic mesoderm lying cranial and lateral to the neural plate
  2. What is the first appearance of the heart in a developing embryo
    Two endothelial lined tubes on the lateral to the of the neural plate on each side
  3. What forms in the lateral folding of the endocardial heart tubes
    The two tubes meet in the ventral midline and fuse together to make a single definitive heart tube
  4. Once the endocardial tubes meet at the ventral end what happens
    The cells separating the tubes undergo apoptosis making them one tube
  5. What is the primitive heart tube composed of after the fusion of the two endocardial tubes
    • Inner endocardial layer (inner lining of heart)
    • Middle layer of cardiac jelly/extracellular matrix proteins
    • Outer myocardial layer (Heart muscle)
  6. Where does the epicardium come from
    Mesodermal cells from near the developing liver, this is the last layer to form in the heart
  7. The primitive heart has what three paired vessels flowing into it
    • Vitelline veins
    • Cardinal veins
    • Umbilical veins
    • All located on the caudal end
  8. What is traveling in the Vitelline veins
    Deoxygenated blood from the yolk sac
  9. What is flowing in the cardinal veins
    Deoxygenated blood from the body of the embryo
  10. What is flowing in the umbilical veins into the heart tube
    Oxygenated blood from the placenta
  11. What does the truncus arteriosus become
    • Aorta
    • Pulmonary trunk
  12. What are the vessels flowing out of the heart tube
    • Truncus arteriosus
    • Aortic arch arteries
  13. When does the heart start beating for the first time
    By day 23 as the heart tube, before its folding
  14. During folding of the heart tube, where does the caudal (atrium) portion go
    It shifts dorsocranially and to the left
  15. During folding of the heart tube, where does the ventricle portion go
    It moves ventrally, caudally, and to the right
  16. What are the layers of the heart tube cranial to caudal before it folds
    • Truncus Arteriosus
    • Bulbos cordis
    • Ventricle
    • Atrium
    • Sinus venosus
  17. When is dextrocardia lethal
    When it is isolated dextrocardia, meaning the organs do not invert their positions as well
  18. What is the transverse pericardial sinus
    It is the the sinus that surrounds the heart (separates the inflow and outflow vessels)
  19. The transverse pericardial sinus develops from
    The degeneration of the dorsal mesocardium connected to the posterior body wall
  20. What does the transverse pericardial sinus become postnatally
    The area behind the aorta and pulmonary trunk used in heart surgery to clamp the aorta and pulmonary artery
  21. What is the direction of blood flow in the heart tube
    Caudal to cranial
  22. What are the two origins of the right atrium
    • Primitive atrium
    • Right horn of the sinus venosus
  23. What happens to the sizes of the sinus venosus after folding
    They are originally the same size but following folding, the right horn sinus becomes larger
  24. Venous return from the body and placenta enter where
    The right atrium
  25. When do the sinus venosus start migrating to form the atrium
    Weeks 4-5
  26. The right horn eventually becomes
    Venae cavae
  27. What happens in week 5 to the left umbilical vein, left vitelline vein, and left sinus horn
    The left umbilical and vitelline are obliterated, and the left horn loses its function
  28. When is the left common cardinal vein obliterated
    Week 10
  29. The remnants of the left sinus horn form the
    Oblique vein of the left atrium and the coronary sinus
  30. What feeds into the coronary sinus
    The inferior venae cavae
  31. What happens if the left horn does not develop properly
    The coronary sinus is not developed and therefore de-oxygenated blood can't return from circulation and a spontaneous abortion will happen
  32. Which part of the left umbilical vein is obliterated
    The proximal end
  33. The trabeculated part of the right atrium develops from
    The original primitive atrium
  34. The smooth portion of the right atrium develops from
    The sinus venosus (smooth portion known as sinus venarum)
  35. The junction between the trabaculated part of the right atrium and the smooth portion is called
    Crista Terminalis
  36. Remodeling of the the left atrium happens
    At the same time as the right atrium
  37. What develops as an outgrowth from the left atrium
    A single pulmonary vein on the posterior wall
  38. What happens to the pulmonary vein that begins an outgrowth from the left atrium
    It divides into four branches, and connects to the blood vessels supplying the developing lungs
  39. How do the proximal branches of the pulmonary branches further develop in the left atrium
    They become incorporated in the posterior wall forming the smooth portion
  40. What forms the rough trabaculae in the left atrium
    The primitive atrium
  41. What is the blood flow in the fetus from placenta to the aorta
    • Placenta
    • Umbilical vein
    • Ductus venosus
    • Inferior Vena cava
    • Right atrium
    • Left atrium
    • Left ventricle
    • Aorta
  42. What are the steps to the formation of the septum
    • Septum primum grows toward endocardial cushions
    • Ostium primum is covered
    • Ostium secundum forms in septum primum
    • Septum secundum begins to form on the right side of the septum primum
    • Septum secundum covers Ostium secundum
    • Septum secundum leaves a hole caudal to Ostium Secundum called foramen ovale
  43. When does the atrial septum begin to form
    4th week
  44. What forms the artial septum
    • Septum primum (Thin membranous)
    • Septum secundum (Thick muscular)
  45. What causes the closure of the foramen ovale
    After birth the pressure in the left atrium is greater then that in the right atrium forcing closure
  46. Where does the Endocardial cushion form
    In between the atriums and ventricles
  47. What is the purpose of the septum primum covering the foramen ovale
    It acts as a rudimentary valve preventing the back flow of blood from the left atrium to the right atrium
  48. What are the five different types of atrial septal defects
    • Probe patent foramen ovale
    • Ostium Secundum effect
    • Endocardial cushion defect w/ ostium primum defect
    • Sinus venosus defect
    • Common atrium
  49. What is the most common Atrial septal defect (ASD)
    Probe patent foramen present in up to 25% of people
  50. What causes probe patent foramen
    Incomplete adhesion of the septum primum flap to the septum secundum
  51. Acyanotic heart defects
    A congenital disorder manifest with left to right shunting and obstructive lesions
  52. What Acyanotic conditions lead to obstruction of blood flow from the ventricles
    • Coarctation of aorta
    • Aortic stenosis
    • Pulmonic stenosis
  53. What are the Acyanotic conditions that have an increase in pulmonary blood flow
    • Atrial septal defect
    • Ventricular septal defect
    • Patent ductus arteriosus
    • Atrioventricular canal
  54. What Cyanotic conditions present with decrease in pulmonary blood flow
    • Tetrology of fallot
    • Tricuspid Atresia
  55. What cyanotic conditions present with mixed blood flow
    • Transposition of great arteries
    • Truncus arteriosus
    • Hypoplastic left heart syndrome
    • Total anomalous pulmonary venous return
  56. What different defects can happen in the Ostium Secundum
    • Perforations of septum primum
    • A small/short septum primum
    • Incomplete septum secundum development
    • Combination of small primum and incomplete secundum
  57. What are the symptoms of those with Ostium secundum defects
    • Fatigue
    • Atrial dysrythmias
    • Systolic murmur
    • Diastolic murmur
  58. In Ostium secundum defects, what causes the Atrial dysrythmias and Systolic murmurs
    • Atrial enlargement
    • Increased blood flow across the pulmonary valve
  59. What happens in an enlarged right atrium to cause atrial arrhythmias
    The size of the atrium irritates the sinus node disrupting the regularity of the heart beat
  60. What happens in an Endocardial cushion defect with ostium primum defect
    • The septum primum doesn't fuse with the endocardial cushions
    • Often is accompanied by a mitral valve defect called mitral valve cleft
  61. What is a mitral valve cleft
    A slit like hole usually in the anterior leaflet of the mitral valve
  62. What is the Sinus venosus defect
    • Results in the incomplete absorption of the sinus venosus into the right atrium and/or abnormal development of the septum secundum
    • Pulmonary veins are often affected as well, being attached to the right atrium instead of the left
  63. Common Atrium (cor tricolare biventriculare)
    • Incomplete development of the atrial septal complex
    • Frequently associated with heterotaxy syndrome (misplaced organs)
  64. What happens in the premature closure of the foramen ovale
    • The left ventricle is not developed like it should be due to less use of it during fetal development
    • Hypertrophy on the right side of the heart
    • Death shortly after birth
  65. The bulbous cordis caudal end forms what
    • The smooth part of the right ventricle (conus arteriosus)
    • The smooth part of the left ventricle
  66. The primitive ventricle forms what
    Trabaculated part of the left and right ventricle
  67. What two structures form the ventricular septum
    • Muscular septum - expansion of myocardium
    • Membranous septum - endocardial cushions and aortico-pulmonary septum
  68. When do the ventricles begin to form
    At the end of the fourth week from the movement of the myocardium
  69. What is left behind in the formation of the interventricular septum
    An interventricular foramen
  70. When does the muscular septal formation stop
    7th week (Does not fuse with the endocardial cushion)
  71. What is the space in between the muscular inter-ventricular septum and cushions
    Inter-ventricular foramen
  72. The membranous portion of the interventricular septum is derived from
    • Right side of the endocardial cushion
    • Tissue form the aorticopulmonary septum
  73. Many ventricular septal defects close spontaneously when
    Within the first year of birth
  74. Ventricular Septal Defects (VSD) are found more in
    Men then in woman
  75. What is the most common VSD, what is it often associated with
    Membranous, aorticopulmonary septum defects
  76. What can a large VSD cause problems with
    • The pulmonary system due to the increase pressure from the left ventricle contraction.
    • Pulmonary hypertension
    • Cardiac failure in infancy
  77. Swiss cheese defects are often found in the less common VSD of
    Muscular VSD
  78. Common ventricle septal defect
    Failure of the membranous and muscular Interventricular septum to form
  79. When do the atrioventricular valves form
    5-8 weeks
  80. What do the Artioventricular valves develop from
    Local proliferations of mesenchyme surrounding the AV orifice
  81. What is the conus cordis
    This is the part of the bulbus cordis that tapers to merge with the truncus arteriosus
  82. What triggers the formation of the AP septum
    Neural crest cells migrating and invading the truncal and bulbar ridges
  83. If the AP doesn't form, what else won't form
    The IV membranous septum
  84. The Aorticopulmonary septum divides what, and connects them to what
    • Truncus arteriosus and the conus cordis into the aorta and pulmonary trunk
    • It also connects the aorta to the left ventricle and the pulmonary to the right ventricle
  85. Persistent truncus arteriosus
    • Failure to separate truncus arteriosus, always associated with VSD
    • Body and lungs receive mixed blood
  86. Transposition of the great vessels
    • Aorta rises from the RV and Pulmonary from the LV
    • More common in males
    • Maternal factors associated with rubella or other viral illness's during pregnancy
    • Can be corrected surgically
  87. What treatment is given to babies found to have transposition of great vessels
    Prostaglandin through IV to keep the ductus arteriosus open, allowing a mixture of blood, and time to do surgery latter
  88. What could cover the affects of transposition of great vessels for several weeks
    A large VSD, due to the blood mixing, allowing some oxygenation in the lungs
  89. What are the four abnormalities in tetralogy of fallot
    • Pulmonary stenosis
    • Ventricular septal defect
    • Overriding aorta
    • Right ventricular hypertrophy caused by higher pressure on the right side
Card Set
Heart Development S1M3