1 Exampromax - Stuvia US 2025/2026
First Aid USMLE Step 1: Cardiovascular Questions with
Detailed Verified Answers (100% Correct Answers)
/Already Graded A+
Truncus arteriosus gives rise to __________.
Ans: Ascending aorta and pulmonary trunk
Bulbus cordis gives rise to __________.
Ans: Smooth parts (outflow tract) of left and right ventricles
Endocardial cushion gives rise to?
Ans: Atrial septum ,membraneous interventricular septum; AV &
Exampromax - Stuvia US
semilunar valves
Approved By:
Primitive atrium gives rise to __________.
Ans: Trabeculated (muscular) portions of the left and right atria
Primitive ventricle gives rise to __________.
Ans: Trabeculated (muscular) portions of the left and right ventricles
Primitive pulmonary vein gives rise to __________.
Ans: Smooth part of the right atrium
Left horn of sinus venosus gives rise to __________.
Ans: Coronary sinus
Right horn of sinus venosus gives rise to __________.
Ans: Smooth part of the right atrium (sinus venarum)
Right common cardinal vein and right anterior cardinal vein gives rise to
__________.
, 2 Exampromax - Stuvia US 2025/2026
Ans: Superior vena cava (SVC)
When does the heart beat begin to beat spontaneously?
Ans: -4 weeks of development
-First functional organ in vertebrate embryos
What is cardiac looping?
Ans: -Primary heart tube loops to establish left-right polarity; begins in
week 4 of gestation.
Defect in left-right dynein (involved in L/R asymmetry) can lead
to___________, as seen in Kartagener syndrome (primary ciliary
dyskinesia).
Exampromax - Stuvia US
Ans: Dextrocardia
Approved By:
What is a foramen/ostium?
Ans: opening
What is a septum?
Ans: wall
Septation of atria (7 Steps)
, 3 Exampromax - Stuvia US 2025/2026
Ans: 1. Septum primum grows toward endocardial cushions, narrowing
foramen primum.
2. Foramen secundum forms in septum primum (foramen primum
disappears).
3. Septum secundum develops as foramen secundum maintains right-to-left
shunt.
4. Septum secundum expands and covers most of the foramen secundum.
The residual foramen is the foramen ovale.
5. Remaining portion of septum primum forms valve of foramen ovale.
6. (Not shown) Septum secundum and septum primum fuse to form the
atrial septum.
7. (Not shown) Foramen ovale usually closes
soon after birth because of increased LA pressure.
Exampromax - Stuvia US
Approved By:
Patent foramen ovale is caused by a failure of __________ and ___________
to fuse after birth. What can this lead to?
Ans: -Caused by failure of septum primum and septum secundum to fuse
after birth; most are left untreated.
-Can lead to paradoxical emboli (venous thromboemboli that enter systemic
arterial circulation), similar to those resulting from an ASD.
Septation of the ventricles (3 steps)
Ans: 1. Muscular ventricular septum forms. Opening is called
interventricular foramen.
2. Aorticopulmonary septum rotates and fuses with muscular ventricular
septum to form membranous interventricular septum, closing
interventricular foramen.
3. Growth of endocardial cushions separates atria from ventricles and
contributes to both atrial septation and membranous portion of the
interventricular septum.
What is the most common congenital cardinal anomaly?
Ans: VSD
, 4 Exampromax - Stuvia US 2025/2026
Most common location of VSD?
Ans: The membranous septum
Outflow tract formation
Ans: Truncus arteriosus rotates; neural crest and endocardial cell
migrations cause truncal and bulbar ridges that spiral and fuse to form
aorticopulmonary septum to form ascending aorta and pulmonary trunk.
What are the conotruncal abnormalities associated w/ failure of neural crest
cells to migrate?
Ans: Transposition of the greta vessels
Tetralogy of Fallot
Exampromax - Stuvia US
Persistent truncus arteriosus
Approved By:
Aortic/pulmonary valves are derived from ____________.
Ans: The endocardial cushions of outflow tract.
Mitral/tricuspid valves are derived from __________.
Ans: Fused endocardial cushions of the AV canal.
Fetal erythropoiesis occurs in ___________?
Ans: -Yolk sac (3-8 weeks)
-Liver (6 weeks-birth)
-Spleen (10-28 weeks)
-Bone marrow (18 weeks to adult)
Hemoglobin development
First Aid USMLE Step 1: Cardiovascular Questions with
Detailed Verified Answers (100% Correct Answers)
/Already Graded A+
Truncus arteriosus gives rise to __________.
Ans: Ascending aorta and pulmonary trunk
Bulbus cordis gives rise to __________.
Ans: Smooth parts (outflow tract) of left and right ventricles
Endocardial cushion gives rise to?
Ans: Atrial septum ,membraneous interventricular septum; AV &
Exampromax - Stuvia US
semilunar valves
Approved By:
Primitive atrium gives rise to __________.
Ans: Trabeculated (muscular) portions of the left and right atria
Primitive ventricle gives rise to __________.
Ans: Trabeculated (muscular) portions of the left and right ventricles
Primitive pulmonary vein gives rise to __________.
Ans: Smooth part of the right atrium
Left horn of sinus venosus gives rise to __________.
Ans: Coronary sinus
Right horn of sinus venosus gives rise to __________.
Ans: Smooth part of the right atrium (sinus venarum)
Right common cardinal vein and right anterior cardinal vein gives rise to
__________.
, 2 Exampromax - Stuvia US 2025/2026
Ans: Superior vena cava (SVC)
When does the heart beat begin to beat spontaneously?
Ans: -4 weeks of development
-First functional organ in vertebrate embryos
What is cardiac looping?
Ans: -Primary heart tube loops to establish left-right polarity; begins in
week 4 of gestation.
Defect in left-right dynein (involved in L/R asymmetry) can lead
to___________, as seen in Kartagener syndrome (primary ciliary
dyskinesia).
Exampromax - Stuvia US
Ans: Dextrocardia
Approved By:
What is a foramen/ostium?
Ans: opening
What is a septum?
Ans: wall
Septation of atria (7 Steps)
, 3 Exampromax - Stuvia US 2025/2026
Ans: 1. Septum primum grows toward endocardial cushions, narrowing
foramen primum.
2. Foramen secundum forms in septum primum (foramen primum
disappears).
3. Septum secundum develops as foramen secundum maintains right-to-left
shunt.
4. Septum secundum expands and covers most of the foramen secundum.
The residual foramen is the foramen ovale.
5. Remaining portion of septum primum forms valve of foramen ovale.
6. (Not shown) Septum secundum and septum primum fuse to form the
atrial septum.
7. (Not shown) Foramen ovale usually closes
soon after birth because of increased LA pressure.
Exampromax - Stuvia US
Approved By:
Patent foramen ovale is caused by a failure of __________ and ___________
to fuse after birth. What can this lead to?
Ans: -Caused by failure of septum primum and septum secundum to fuse
after birth; most are left untreated.
-Can lead to paradoxical emboli (venous thromboemboli that enter systemic
arterial circulation), similar to those resulting from an ASD.
Septation of the ventricles (3 steps)
Ans: 1. Muscular ventricular septum forms. Opening is called
interventricular foramen.
2. Aorticopulmonary septum rotates and fuses with muscular ventricular
septum to form membranous interventricular septum, closing
interventricular foramen.
3. Growth of endocardial cushions separates atria from ventricles and
contributes to both atrial septation and membranous portion of the
interventricular septum.
What is the most common congenital cardinal anomaly?
Ans: VSD
, 4 Exampromax - Stuvia US 2025/2026
Most common location of VSD?
Ans: The membranous septum
Outflow tract formation
Ans: Truncus arteriosus rotates; neural crest and endocardial cell
migrations cause truncal and bulbar ridges that spiral and fuse to form
aorticopulmonary septum to form ascending aorta and pulmonary trunk.
What are the conotruncal abnormalities associated w/ failure of neural crest
cells to migrate?
Ans: Transposition of the greta vessels
Tetralogy of Fallot
Exampromax - Stuvia US
Persistent truncus arteriosus
Approved By:
Aortic/pulmonary valves are derived from ____________.
Ans: The endocardial cushions of outflow tract.
Mitral/tricuspid valves are derived from __________.
Ans: Fused endocardial cushions of the AV canal.
Fetal erythropoiesis occurs in ___________?
Ans: -Yolk sac (3-8 weeks)
-Liver (6 weeks-birth)
-Spleen (10-28 weeks)
-Bone marrow (18 weeks to adult)
Hemoglobin development
