Embryology: heart: practice question

A Anatomy question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

Try it

Anatomy · Embryology: heart

Sample item

A 6-year-old has an ejection systolic murmur at the left upper sternal edge and fixed splitting of the second heart sound. Echocardiography shows an ostium secundum atrial septal defect. What is the embryological defect?

AFailure of the endocardial cushions to fuseBFailure of the aorticopulmonary septum to spiralCIncomplete incorporation of the right sinus horn into the atriumDExcessive resorption of the septum primum or deficient septum secundum

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. Excessive resorption of the septum primum or deficient septum secundum

Ostium secundum defects, the commonest atrial septal defect, lie in the region of the fossa ovalis. They result from excessive resorption of the septum primum or inadequate growth of the septum secundum. Left-to-right shunt volume loads the right heart and causes fixed splitting of the second sound.

Option by option

A. Failure of the endocardial cushions to fuse
Defective cushion fusion causes ostium primum defects and atrioventricular septal defects, common in Down syndrome.
B. Failure of the aorticopulmonary septum to spiral
This gives transposition or persistent truncus arteriosus, not an atrial defect.
C. Incomplete incorporation of the right sinus horn into the atrium
This causes a sinus venosus defect near the superior vena cava.
D. Excessive resorption of the septum primum or deficient septum secundum (correct)
Correct. A secundum defect arises from excessive resorption of the septum primum or deficient septum secundum.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Anatomy question

What is the answer to this Anatomy question?

The best answer is D, Excessive resorption of the septum primum or deficient septum secundum. Ostium secundum defects, the commonest atrial septal defect, lie in the region of the fossa ovalis.

Why is "Failure of the endocardial cushions to fuse" not the answer?

Defective cushion fusion causes ostium primum defects and atrioventricular septal defects, common in Down syndrome.

Why is "Failure of the aorticopulmonary septum to spiral" not the answer?

This gives transposition or persistent truncus arteriosus, not an atrial defect.

Why is "Incomplete incorporation of the right sinus horn into the atrium" not the answer?

This causes a sinus venosus defect near the superior vena cava.

What concept does this question test?

It tests Embryology: heart in Anatomy. They result from excessive resorption of the septum primum or inadequate growth of the septum secundum. Left-to-right shunt volume loads the right heart and causes fixed splitting of the second sound.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Embryology: heart?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.