**Question:** Which of the following is true about right principal bronchus?

A. It is the largest bronchus in the lungs
B. It branches into two lobar bronchi: right posterior and right anterior bronchi
C. It is shorter than the left principal bronchus
D. It is the only bronchus without a mucus gland

**Core Concept:** The right principal bronchus is a part of the respiratory system, specifically referring to the bronchus that carries air to the right lung.

**Why the Correct Answer is Right:**

Correct Answer: **B. It branches into two lobar bronchi: right posterior and right anterior bronchi.**

The right principal bronchus (RBB) branches into two lobar bronchi: the right posterior bronchus (RpB) and the right anterior bronchus (RaB). These bronchi further branch into segmental bronchi and subsegmental bronchi, which distribute air to the right lung's different lobes and segments.

**Why Each Wrong Option is Invalid:**

A. **It is the largest bronchus in the lungs:** This is incorrect because, despite being the right principal bronchus, it is not the largest bronchus in the lungs. The largest bronchus is the trachea, followed by the left principal bronchus, then the right principal bronchus, and finally the right and left secondary bronchi.

C. **It is shorter than the left principal bronchus:** This statement is false, as the left principal bronchus is generally shorter than the right one. However, the length of the bronchi can vary between individuals, so this is not universally true.

D. **It is the only bronchus without a mucus gland:** This statement is incorrect as all bronchi have mucus glands lining their inner walls. The glands secrete mucus to protect the airways from irritants, maintain lung moisture, and facilitate ciliary movement for efficient mucociliary escalator function.

**Clinical Pearl:** Understanding bronchial anatomy is essential for diagnosing and treating respiratory disorders. A knowledge of bronchial branching helps determine the location of lung lesions, assess lung function, and guide clinical interventions, such as bronchoscopy procedures or bronchial tree resections.