Learning Objective

By the end of this topic, the learner should be able to identify major embryonic cardiac structures, describe the adult cardiac and vascular components they form, and apply these relationships to congenital and clinical correlations.

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Heart Embryology: Embryonic Structures and Adult Derivatives

Venous System

• Right common cardinal vein + right anterior cardinal vein
  → Superior vena cava (SVC)
• Posterior cardinal, subcardinal, and supracardinal veins
  → Inferior vena cava (IVC)

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Sinus Venosus Derivatives

• Right horn of the sinus venosus
  → Smooth part of right atrium (sinus venarum)
• Left horn of the sinus venosus
  → Coronary sinus

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Atrial Structures

• Primitive pulmonary vein
  → Smooth part of the left atrium
• Primitive atrium
  → Trabeculated portions of both atria

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Septal and Valve Development

• Endocardial cushions
  → Atrial septum
  → Membranous interventricular septum
  → Atrioventricular and semilunar valves

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Ventricular Structures

• Primitive ventricle
  → Trabeculated portions of both ventricles
• Bulbus cordis
  → Smooth outflow tracts of left and right ventricles

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Great Vessels

• Truncus arteriosus
  → Ascending aorta
  → Pulmonary trunk

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Timeline of Early Heart Development

• Day 22: Heart tube formation begins
• Day 24: Cardiac looping
• Day 35: Septation in progress
• Day 50: Near-complete chamber formation

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Exam Tip

• Smooth atrial walls = sinus venosus (right) or pulmonary vein (left)
• Trabeculated atria and ventricles = primitive atrium and primitive ventricle
• Outflow tract defects → think bulbus cordis or truncus arteriosus

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