Choose the appropriate lettered site or structure in this CT scan of the thorax. Becomes hypertrophied as result of the pulmonary stenosis?

**Core Concept**
The question is testing the understanding of the anatomical and physiological changes that occur in response to pulmonary stenosis, a condition characterized by the narrowing of the pulmonary valve. The correct answer will reveal the structure that hypertrophies as a result of this condition.

**Why the Correct Answer is Right**
In pulmonary stenosis, the increased pressure and resistance to blood flow through the pulmonary valve lead to hypertrophy of the right ventricular muscle. This is because the right ventricle must work harder to pump blood through the narrowed valve, resulting in an increase in muscle mass. The right ventricle is a crucial structure in the heart, responsible for pumping blood from the right atrium to the lungs for oxygenation.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the condition of pulmonary stenosis. The tricuspid valve is located between the right atrium and the right ventricle and is not directly affected by pulmonary stenosis.
* **Option B:** The left ventricular muscle is not directly affected by pulmonary stenosis, as the condition primarily involves the right side of the heart.
* **Option C:** The septal wall of the heart is not a structure that hypertrophies in response to pulmonary stenosis. The septal wall is a thin layer of tissue that separates the left and right ventricles.

**Clinical Pearl / High-Yield Fact**
In conditions of increased pressure and resistance, such as pulmonary stenosis, the affected ventricle will hypertrophy in an attempt to compensate for the increased workload. This is a critical concept to understand in cardiology, as it can be used to diagnose and manage various cardiac conditions.

**Correct Answer: C. Right ventricular muscle.**