Features of Week 5
Primitive ventricle with partial muscular ventricular septum
Bulbus cordis and truncus arteriosus (which comprise the outflow tract)
Arioventricular septum and canals connect atria and ventricle.
Right and left conotruncal ridges as they arise from the walls of the outflow tract and form a spiral configuration.
- Their helical form reflects the flow of low oxygen and high oxygen blood through the heart.
- Swellings grow towards each other, pinching the single lumen.
Heart Development - Outflow Tract & Ventricle Septa
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Division of the outflow tract and ventricle occurs between weeks 5 and 9.
- The outflow tract is divided by the aorticopulmonary septum.
- This partition begins to form when second heart field and cardiac neural crest cells migrate to the elongating heart.
- The primitive ventricle is divided by a septum comprised of muscular and membranous portions.
- The muscular interventricular septum forms as the ventricle itself expands.
- The membranous septum comprises the lower portion of the spiral aorticopulmonary septum and the ventricular side of the atrioventricular endocardial cushions.