Flashcards in CVS Session 3- Early Development Of The CVS 2 Deck (17)
When does septation occur?
End of week 4 of development
What is septation?
The process of dividing
Describe atrioventricular septation.
-endocardial cushions form on the dorsal and ventral aspects of the atrioventricular canal.
-these cushions grow towards each other and fuse, completely dividing the atria from the ventricles.
What does division of the common atria involve?
The formation of 2 septa and 3 holes.
Describe atrial septation.
-the septum premium grows down from the roof of the atria to the endocardial cushions that have fused.
-the ostium primum is formed before the septum primum fuses with the endocardial cushions.
-the ostium secundum begins to appear in the septum primum before the ostium primum closes.
-a crescent shaped septum called the septum secundum begins to grow from the roof of the atria towards the endocardial cushions. The hole in this septum is called the foreamen ovale.
What does atrial septation allow?
A right to left shunting thought the foreamen ovale and ostium secundum.
What happens to the foreamen ovale at birth? How does this occur? Why does this occur?
It closes to form a depression in the right atrium called the fossa ovalis.
This happens due to respiration at birth which causes the left atrial pressure to be greater than the right atrial pressure, therefore forcing the septum primum to be pushed against the septum secundum and therefore close the foreamen ovale.
Describe ventricular septation.
It has a membranous and a muscular component.
A muscular component grows upwards from the ventricular wall towards the endocardial cushion, but leaves a gap called the primary interventricular foreamen.
A membranous part of the endocardial cushions then grows down to meet the muscular component and close this gap.
Describe conotruncal septation.
It is the division of the truncus arteriosus into the aorta and pulmonary trunk channels.
This occurs by the growth of endocardial cushions in the truncus arteriosum which grow towards and twist around each other to form a spiral septum called the aorticopulmonary septum.
Which shunt by passes the liver?
The ductus venosus
Which shunts bypass the lungs?
Foreamen ovale and the ductus arteriosum.
Where is the ductus arteriosus found?
Between the pulmonary trunk and the aorta.
Where is the foreamen ovale found?
Between the left and right atria.
What is the fate of the ductus venosus at birth?
Becomes the ligamentum venosum.
What is the fate of the ductus arteriosus at birth?
Becomes the ligamentum arteriosum.
What is the fate of the foreamen ovale at birth?
Becomes the fossa ovalis.