Final answer:
In patients with ventricular septal defects and left-to-right shunting, the right atrium and right ventricle may become dilated due to the increased blood flow from left to right across the defect.
Step-by-step explanation:
In patients with ventricular septal defects and left-to-right shunting, the right atrium and right ventricle may be dilated because of the increased flow of blood from the left side of the heart to the right side. It is important to understand the normal flow of blood in the heart to grasp the effects of such defects. Normally, blood from the systemic circuit enters the right atrium, goes through the right ventricle, and is then pumped to the lungs for oxygenation before entering the left atrium and left ventricle to be circulated throughout the body. When a ventricular septal defect is present, there is an abnormal communication between the right and left ventricles, allowing blood to flow from the higher pressure left ventricle to the lower pressure right ventricle, leading to dilation.
The pulmonary trunk and aorta are derived from the truncus arteriosus, and the right ventricle arises from the bulbus cordis. It is false that blood travels through the bicuspid valve (mitral valve) to the left atrium; instead, it travels from the left atrium to the left ventricle.