Home › DHA Nursing Licensing Exam › Anatomy & Physiology › Heart Anatomy › In the fetus, an opening in the interatrial sept…
In the fetus, an opening in the interatrial septum lets blood bypass the pulmonary circuit. What seals it after birth?
AThe chordae tendineae contract firmly
BA flap called the septum primum closes
CThe tricuspid valve fuses shut
DThe moderator band tightens
Answer & Solution
Correct answer: B. A flap called the septum primum closes
1. Fetal lungs are not breathing, so some blood bypasses the pulmonary circuit through the interatrial septum.
2. Within seconds after birth, a flap of tissue known as the septum primum closes the opening.
3. Valves and bands play no role in sealing the septum, which removes the other options.
4. The interventricular septum, by contrast, is complete well before birth.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 19 "The Cardiovascular System: The Heart", section 19.1 Heart Anatomy_
Related questions
The right ventricle pumps its blood into which circuit?The flaps of the atrioventricular valves connect to papillary muscles through which structWhich valve guards the opening between the left atrium and the left ventricle?Blood passing from the right atrium into the right ventricle crosses which valve?The valves lying between the atria and the ventricles are known generically as what?What is the name of the wall that separates the two atria?Why must the left ventricle generate much more pressure than the right?The systemic circuit delivers oxygenated blood to which destination?