questions 5

Cardiac Development

Topic updated on 01/06/17 5:02pm

embryonic structures
  • Heart development
    • 5 dilatations along primitive heart tube forms into adult heart structures
    • dextral looping of the primitive heart aligns the heart chambers and structures
    • septum and valves develop which allow for separation of the venous and arterial circulatory pathways
    • heart begins beating during week 4
Embryonic structures
Embryonic structure
Adult structure
Truncus arteriosus
  • Ascending aorta
  • Pulmonary trunk
Bulbus cordis
  • Smooth part of left and right ventricle
Primitive ventricle
  • Trabeculated part of left and right ventricle
Primitive atria
  • Trabeculated part of left and right atrium
Sinus venosus
  • Coronary sinus
  • Smooth part of right atrium
Right common and right anterior cardinal vein  
  • SVC
  • Truncus arteriosus 
    • neural crest cells migrate from hindbrain to aorticopulmonary (AP) trunk
      • cells invade truncal and bulbar ridges
      • the ridges then twist, spiral, and fuse to form the AP septum dividing the AP trunk into the ascending aorta and pulmonary trunk
  • Persistent truncus arteriosus
    • partial development of AP septum resulting in mixing of oxygenated and deoxygenated blood leading to cyanosis
  • Transposition of great vessels (transposition of great arteries)
    • ridges do not spiral as they develop resulting in two separate circulatory pathways
      • aorta arises from right ventricle
      • pulmonary arises from left ventricle  
    • blood never gets oxygenated which will result unless there is a shunt between the two pathways
      • VSD, patent foramen ovale, or PDA
  • Tetralogy of Fallot
    • skewed development of AP septum resulting in
      • Pulmonary stenosis
      • Right ventricular hypertrophy
      • Overriding aorta
      • VEntricular septal defect
    • cyanosis but severity depends on degree of pulmonary stenosis
Interventricular septum development

interventricular septum2

  • Muscular ventricular septum
    • forms from the floor of the primitive ventricle 
    • opening between muscular ventricular septum and fused AV cushions is called interventricular foramen
    • AP septum then fuses with muscular ventricular septum to form the membranous interventricular septum
  • Common ventricle
    • muscular and membranous interventricular septum do not form
  • Membranous septal defect
    • failure of the membranous interventricular septum to form properly
    • blood flows from left to right due to higher pressure in systemic circulatory system
    • as a result pulmonary hypertension develops
      •  the lumen of pulmonary arteries and arterioles narrow due to proliferation of the tunica media and intima
    • pulmonary resistance then becomes greater than systemic reversing the flow of blood across the opening
    • the resulting condition is called Eisenmenger complex
Interatrial septum development

interatrial septum

  • Septum primum
    • grows downward from the superior part of the primitive atrium
    • as the septum primum nears the atrioventricular cushions, new openings form at the center creating the foramen secundum
    • foramen secundum allows for shunting of the blood from right to left
  • Septum secundum
    • grows downward and covers the foramen secundum leaving an opening inferiorly 
    • superior portion of septum primum degenerates
    • inferior portion of septum primum and septum secundum form the foramen ovale
    • foramen ovale remains open until birth
    • at birth, right atrial pressure decreases and left aftrial pressures increases due to increased pulmonary blood flow into left atrium resting in the closure of the foramen ovale
  • Patent foramen ovale
    • foramen ovale does not close due to excessive resoprtion of septum primum, secundum, or both



Qbank (3 Questions)

(M1.EB.29) A patient in the neonatal intensive care unit develops severe cyanosis. Cardiac exam reveals a single loud S2 with a right ventricular heave. Echocardiography reveals an aorta lying anterior and right of the pulmonary artery. Which of the following processes failed during fetal development? Topic Review Topic

1. Fusion of the membranous ventricular septum
2. Septation of spiraling truncus arteriosus
3. Ectopic ductal tissue tightening
4. Reentry of viscera from yolk sac
5. Fusion of septum primum and septum secondum

(M1.EB.62) A 69-year-old smoker presents to physician after noticing that his face seems to be more swollen than usual. Upon further questioning, he reports increasing shortness of breath and cough over the past 6 months. On exam, his physician notices venous distention in his neck and distended veins in the upper chest and arms. Chest radiograph shows a right upper lobe mass. What is the embryologic origin of the vessel being compressed by this patient's tumor? Topic Review Topic

1. Truncus arteriosus
2. Bulbis cordis
3. Primitive ventricle
4. Left horn of sinus venosus
5. Cardinal veins

(M1.EB.62) After receiving no prenatal care during her pregnancy, a 29-year-old woman gives birth to a full term male. Shortly after delivery the infant becomes cyanotic. Pulse oximetry is placed on upper and lower extremities. It reads <90% in all locations and oxygen saturation is unchanged with administration of 100% supplemental oxygen. An echocardiogram is performed and demonstrates the aorta lying anterior and to the right of the pulmonary artery. What typically occurs during fetal development that leads to the above congenital heart defect? Topic Review Topic

1. Incomplete formation of septum secundum
2. Failure of the aorticopulmonary septum to spiral
3. Incomplete formation of ostium primum
4. Failure of interventricular septation
5. Failure of ductus arteriosus closure

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Early heart development and folding of the primitive heart tube
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