What is the membranous portion of the interventricular septum formed by?
Connective tissue derived from endocardial cushions
What does the membraneous portion of the interventricular septum do?
Fills the primary interventricular foramen
Where do endocardial cushions appear?
In the truncus arteriosus
What happens as endocardial cushions grow?
They twist around each other, forming a spiral septum
What is formation of the twisted endocardial cushions dependant on?
Contribution from the neural crest
Where does the neural crest migrate from?
Outside of the cardiogenic field
What is present before endocardial cushions appear?
A right and left channels
What happens to the left and right channels when endocardial cushions appear?
It creates a spiral divisions of the outflow tract
What does the spiral division of the outflow tract create?
The ability to separate outflow of the left ventricle from the right ventricle, and divert it to the appropriate site
What is the spiral arrangement of the outflow tract the reason for?
The aorta and pulmonary trunk seem to wrap around each other
What happens after birth?
Respiration begins, opening the pulmonary circulation
What is the result of the opening of the pulmonary circulation?
Left atrial pressure increases, and so forces the foramen ovale closed
What happens to the ductus arteriosus after birth?
It contracts in the presence of the higher oxygen saturation
What happens to the contraction of the ductus arteriosus over time?
It becomes an anatomical contraction, making this vessel fibrotic
What happens when the placental support is removed?
The ductus venous closes as there is no blood flowing through it
Why does the foramen ovale close at birth
Because the LA pressure is greater than the RA pressure, so the septum primum is pushed against the septum secundum, and so blood cannot pass through
What does the foramen ovale become?
The fossa ovalis
What does the ductus arteriosus become?
The ligamentum arteriosum
What does the ductus venosus become?
The ligamentum venosum
What does the umbilical vein become?
The ligamentum teres