Block 1 - Embryology - The Heart Flashcards
What are the three most basic locations for septa formation during cardiac development?
Between the atria, between the ventricles, and to divide the truncus arteriosus
Describe the appearance of the embryonic heart once the truncus arteriosus is formed.
What two structures does the endocardial cushion divide and separate during embryonic development?
The atria from the ventricles
What part of the interventricular septum forms first, the muscular or membranous?
Muscular (growing superiorly from the inferior portion of the heart)
When the first interatrial septum forms, what space is left in the septum?
What is its purpose?
The foramen primum;
to allow right-to-left shunting so the blood bypasses the immature lungs
Just before closure of the foramen primum, what structure develops next?
What is its purpose?
The foramen secundum;
to maintain the right-to-left shunt
What structure extends to cover the foramen secundum during embryonic cardiac development?
What is the name of the remaining exposed portion of the foramen secundum?
The septum secundum;
the foramen ovale
What is important about the foramen ovale valve created by the foramen secundum and septum secundum?
It creates a one-way, flutter valve through which blood can only flow right-to-left through the foramen ovale;
left-to-right flow should close the valve
(this will become important when the lungs become active and pressures within the heart change)
What embryonic structure gives rise to the aorta and pulmonary trunk?
Around what septum does it twist to form these two structures?
The truncus arteriosus;
the (spiral-shaped) aorticopulmonary septum
What is unique about the aorticopulmonary septum?
It is spiral-shaped
What must happen to divide the truncus arteriosus into the aorta and pulmonary trunk?
The aorticopulmonary septum must form
What is the benefit of the aorticopulmonary septum being spiral-shaped?
It allows for the blood from the right and left ventricles to easily bypass one another without mixing
In fetal circulation, where does blood from the ductus venosus tend to flow once it reaches the right atrium?
Is this blood oxygenated or not?
It tends to flow across the atrium into the foramen ovale (bypassing the lungs);
it comes from the umbilical vein, which is the most well-oxygenated blood in all the fetus (0.8 SaO2)
Why does the ductus arteriosus typically close once the neonate begins breathing?
What medication can also cause this reaction in cases of patent ductus arteriosus?
An increase in oxygen saturation leads to a decrease in prostaglandins synthesis;
indomethacin (an NSAID)
Why does the foramen ovale typically close once the neonate begins breathing?
An increase in blood flow to the lungs leads to increased return to the left atrium and increased left atrial pressure.
The valve of the foramen ovale is a one-way, flutter valve, and so it is forced closed as the pressure in the left atrium surpasses the pressure in the right atrium
