primitive heart tube

• What is the name of the mesodermal region from which the heart develops?

  • Cardiogenic area
• What shape does the cardiogenic area form?

  Horseshoe-shaped structure
• What type of mesoderm does the cardiogenic area differentiate into?

  • Cardiogenic mesoderm
  • Splanchic mesoderm (associated with the developing gut)
• What are the two regions into which the cardiogenic area is subdivided?

  • Primitive heart field
  • Secondary heart field
• What structures does the primitive heart field give rise to?

  • Myocardium (muscular heart wall)
  • Endocardium (inner lining of the heart)
• What additional heart structures does the secondary heart field contribute to?

  • Outflow tract
  • Right ventricle
  • Atria
• What are endocardial tubes and what are their precursors?

  • Paired longitudinal endothelial-lined tubes formed from cardiogenic mesoderm
  • Precursors to the heart chambers
• What occurs at approximately day 21-22 in the development of the heart?

  Fusion of the endocardial tubes to form the primitive heart tube
• What will the lumen of the fused primitive heart tube eventually become?

  • The heart chambers
• What is the C-shaped bend called that is formed during the looping of the heart tube?

  Cardiac loop
• In which direction do the atria and ventricles move during the bending and looping of the heart tube?

  • Atria move to the back
  • Ventricles move to the front
• What structure does the primitive ventricle become?

  Left ventricle
• From which part of the heart tube does the right ventricle and part of the outflow tract arise?

  Bulbus cordis
• What structures does the primitive atrium become?

  Right and left atria
• What important process occurs along with the bending and twisting of the heart tube?

  • Formation of the septum to divide the heart into left and right sides
  • Development of heart valves
  • Formation of the outflow tract
• What are endocardial cushions and what role do they play in heart development?

  • Composed of mesodermal cells that migrate into the lumen of the heart tube
  • Critical role in development of heart valves and septa
• What septa begin to form during endocardial cushion development?

  Atrial septum and ventricular septum
• Name the two septa that also develop during endocardial cushion development.

  Atrioventricular septum and outflow tract septum
• What is the initial role of the primitive heart tube after it begins to pump blood?

  • Circulating the embryo’s blood through the yolk sac and developing body