Embryology-CV Developmental Abnormalities Flashcards
In the embryonic heart, the crista terminals separates what two structures?
Sinus venosus and embryonic atrium.
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What structure is located in the crista terminalis?
SA node.
How does fetal blood flow circulate?
Umbilical vein -> ductus venosus bypasses liver -> IVC/SVC -> foramen ovale and foramen secundum bypass right ventricle -> left atrium -> left ventricle -> aorta. Blood that does go through the right ventricle goes through the pulmonary artery and into the aorta, bypassing the lungs.
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When do most congenital heart defects form?
Weeks 3-8. This is because the heart is forming at this period and often, mothers don’t even know they’re pregnant at this point.
What is the most common cause of congenital heart defects?
Trisomy 21. AV septal and valve defects.
What environmental factors can cause congenital heart defects?
Congenital rubella infection, gestational diabetes and teratogens.
What are the main categories of congenital heart defects?
Left to right shunt, right to left shunt and obstruction
Atresia
blockage or absence of a normal opening
Overriding aorta
Instead of arching to the left the aorta is displaced to the right so that it appears to arise from both ventricles.
Why wouldn’t a left to right ASD cause blue baby?
Because oxygenated blood is being shunted away and tissues continue to get oxygenated blood.
In an adult there is a hole in the atrial septum. What structure is absent?
Septum secundum. It is the second wall that divides the atria into two sides.
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What abnormalities can cause formation of an atrial septal defect?
1) Excessive resorption of the septum primum 2) Large formation of oval foramen caused by a short septum primum 3)Septum secundum does not form 4) Common atrium
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Why would someone really want their ASD corrected?
Blood clots are likely to form in the right atrium. Smaller blood clots are not as big of a problem in the lungs. If the clot can get into the left atrium, a smaller clot can easily cause a stroke.
Developmental defects in the endocardial cushions can result in what congenital heart defects?
ASD (foramen primum does not close), VSD (IV septum does not close) and AVSD (atrioventricular septum is open)
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What portions of the AV valves would be absent in an AVSD?
The septal leaflet of the tricuspid and anterior leaflet of the mitral valve.
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