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CARDIOvASCuLAR ``CARdIOvASCulAR—EMbRYOlOGY CARDIOvASCuLAR ``CARdIOvASCulAR—EMbRYOlOGY SECTION III 281

Heart morphogenesis (continued)
Ventricles Muscular interventricular septum forms. Ventricular septal defect—most common
Opening is called interventricular foramen. congenital cardiac anomaly, usually occurs in
Aorticopulmonary septum rotates and fuses membranous septum.
with muscular ventricular septum to form
membranous interventricular septum, closing
interventricular foramen.
Growth of endocardial cushions separates
atria from ventricles and contributes to both
atrial septation and membranous portion of
the interventricular septum.

Aorticopulmonary
septum

RA LA RA LA RA LA
Interventricular
foramen
Membranous
Atrioventricular interventricular
canals septum
Muscular
interventricular
septum
Outflow tract Neural crest and endocardial cell migrations Conotruncal abnormalities associated with
formation Ž truncal and bulbar ridges that spiral failure of neural crest cells to migrate:
and fuse to form aorticopulmonary septum ƒ Transposition of great vessels.
Ž ascending aorta and pulmonary trunk. ƒ Tetralogy of Fallot.
ƒ Persistent truncus arteriosus.
Valve development Aortic/pulmonary: derived from endocardial Valvular anomalies may be stenotic, regurgitant,
cushions of outflow tract. atretic (eg, tricuspid atresia), or displaced (eg,
Mitral/tricuspid: derived from fused endocardial Ebstein anomaly).
cushions of the AV canal.

Heart embryology EMbRYONIC STRuCTuRE GIvES RISE TO
Truncus arteriosus Ascending aorta and pulmonary trunk
Bulbus cordis Smooth parts (outflow tract) of left and right
ventricles
Primitive ventricle Trabeculated part of left and right ventricles
Primitive atrium Trabeculated part of left and right atria
Left horn of sinus venosus Coronary sinus
Right horn of sinus venosus Smooth part of right atrium (sinus venarum)
Endocardial cushion Atrial septum, membranous interventricular
septum; AV and semilunar valves
Right common cardinal vein and right anterior Superior vena cava (SVC)
cardinal vein
Posterior, subcardinal, and supracardinal veins Inferior vena cava (IVC)
Primitive pulmonary vein Smooth part of left atrium

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