Which structure identifies the right ventricle?

• A. Coronary sinus
• B. Pulmonary vein
• C. Sinus venosus
• D. Moderator band

Answer: (D)

The structure that identifies the right ventricle is the moderator band, also called the septomarginal trabecula. It is a prominent muscular band spanning the right ventricular cavity from the interventricular septum to the base of the anterior papillary muscle and, importantly, it carries part of the conduction system (the right bundle branch) to coordinate RV contraction. This feature is characteristic of the right ventricle and helps distinguish it from the left ventricle, which lacks this structure. The other options lie in the right atrium or left atrium: the coronary sinus drains the right atrium; the pulmonary veins empty into the left atrium; and the sinus venosus is a fetal and atrial structure.