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Formation of the Right and Left Atria - Coggle Diagram
Formation of the Right and Left Atria
Septum Primum:
Descends from the roof of the atrium, partially separating the atrium into right and left sides.
Ostium Primum
An opening near the base of the atrium that remains after the septum primum forms.
Closure of Ostium Primum
Endocardial Cushions:
Derived from neural crest cells, they pinch together to narrow the ostium primum.
Apoptosis
: Cells of the septum primum undergo apoptosis, creating the ostium secundum.
Formation of Ostium Secundum
Ostium Secundum:
Forms as the ostium primum closes, allowing blood flow between the atria.
Blood Flow:
Well-oxygenated and poorly-oxygenated blood flow through the ostium secundum.
Expansion of the Atria
Right Atrium Expansion:
Pulls the wall of the sinus venosus, creating the septum spurium.
Left Atrium Expansion:
Pulmonary veins are pulled into the expanding wall of the left atrium.
Formation of Foramen Ovale
Septum Secundum:
Develops to the right of the septum primum and covers the ostium secundum.
Foramen Ovale:
A hole in the septum secundum that allows blood flow from the right to the left atrium.
V
alve of Foramen Ovale
: A section of the septum primum that acts as a valve for the foramen ovale.
Blood Flow Through Foramen Ovale
I
nferior Vena Cava:
Blood pushes the valve of the foramen ovale out of the way.
At Birth:
The valve shuts the foramen ovale, closing the passage.
Atrial Septal Defects (ASD)
Types of ASD:
Ostium Secundum
: Most common, affects the midportion of the atrial septum.
Ostium Primum:
Affects the lower portion of the atrial septum.
Sinus Venosus
: Affects the junction of the right atrium and vena cava.
Symptoms
: Small defects may be asymptomatic or produce a slight murmur. Larger defects can cause a wide fixed split S2 murmur.
Patent Foramen Ovale (PFO)
Pathology
: Frequently asymptomatic, but can open during increased right heart pressure.
Complications
: Can allow thromboemboli to enter the arterial circulation, potentially causing a stroke.