Truncus arteriosus is characterized by:

Truncus arteriosus is characterized by:

• A. Pulmonary arteries are abnormally merged with the aorta
• B. The aorta and pulmonary artery are normally separate
• C. There is no ventricular septal defect
• D. Systemic blood flow is normal

Answer: (A)

Truncus arteriosus involves a single arterial trunk exiting the heart that gives rise to both the systemic (aorta) and pulmonary arteries because the embryologic outflow tract fails to divide. This creates one common vessel rather than two separate great arteries, so the pulmonary arteries are abnormally merged with the aorta. A ventricular septal defect is typically present, allowing mixing of blood from the two ventricles, which affects how blood is distributed to the body and lungs. Systemic blood flow is not normal in this condition due to this mixing and the abnormal distribution of flow to the pulmonary circulation. So the defining feature is a single trunk that supplies both the aorta and pulmonary arteries.

Truncus arteriosus involves a single arterial trunk exiting the heart that gives rise to both the systemic (aorta) and pulmonary arteries because the embryologic outflow tract fails to divide. This creates one common vessel rather than two separate great arteries, so the pulmonary arteries are abnormally merged with the aorta. A ventricular septal defect is typically present, allowing mixing of blood from the two ventricles, which affects how blood is distributed to the body and lungs. Systemic blood flow is not normal in this condition due to this mixing and the abnormal distribution of flow to the pulmonary circulation. So the defining feature is a single trunk that supplies both the aorta and pulmonary arteries.