Which of the following structures is derived from the truncus arteriosus?

Explanation

## Embryological Origin of the Truncus Arteriosus **Key Point:** The truncus arteriosus is the embryonic arterial trunk that divides during weeks 4–6 of development to form the pulmonary trunk and the ascending aorta. ### Division of the Truncus Arteriosus The truncus arteriosus is partitioned by the **aorticopulmonary septum** (a spiral septum derived from neural crest cells) into two main arterial trunks: 1. **Pulmonary trunk** — carries deoxygenated blood to the lungs (via right and left pulmonary arteries) 2. **Ascending aorta** — carries oxygenated blood systemically ### Embryological Timeline | Week | Event | | --- | --- | | 4–5 | Aorticopulmonary septum begins to form | | 5–6 | Septation complete; truncus arteriosus divided | | 6–7 | Aortic arches remodel; definitive arterial pattern emerges | **High-Yield:** The **spiral orientation** of the aorticopulmonary septum is clinically important — abnormal septation leads to **transposition of the great arteries (TGA)** and **tetralogy of Fallot (TOF)**. **Clinical Pearl:** Defects in neural crest cell migration during truncus arteriosus division are associated with **DiGeorge syndrome (22q11 deletion)**, which presents with conotruncal heart defects, thymic hypoplasia, and cleft palate. ### What the Truncus Arteriosus Does NOT Form - ~~Aortic arch~~ — derived from aortic arch arteries (pharyngeal arch arteries) - ~~Superior and inferior vena cava~~ — derived from cardinal veins and sinus venosus - ~~Coronary arteries~~ — arise as outgrowths from the aortic sinuses