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



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