**Question:** True about right principal bronchus?

A. It is the largest bronchus in the body.
B. It is responsible for supplying oxygen to the right lower lobe of the lung.
C. It is the first branch of the trachea.
D. It is the longest bronchus in the body.

**Correct Answer:**

**Core Concept:** The right principal bronchus refers to the primary bronchus that branches off the trachea and carries air to the right lung. In the right lung, air is distributed to two lobes: the upper lobe and the lower lobe.

**Why the Correct Answer is Right:**

The correct answer is correct because the right principal bronchus (Option C) is indeed the first branch of the trachea and supplies oxygen to the right lower lobe of the lung. The right upper lobe is supplied by the right upper lobe bronchus, which is a branch of the right main bronchus.

**Why Each Wrong Option is Incorrect:**

A. The right principal bronchus is not the largest bronchus in the body. This is incorrect as the largest bronchus belongs to the left lung, supplying the two lobes.
B. The right principal bronchus is not responsible for supplying oxygen to the right lower lobe only. As explained, it supplies the right lower lobe, but also the right lingula, a minor division of the right main bronchus, which further branches into the right upper lobe bronchus.
D. The right principal bronchus is not the longest bronchus in the body. The longest bronchus belongs to the left lung, supplying the two lobes.

**Clinical Pearl:** Understanding bronchial anatomy is crucial for accurate diagnosis and management of respiratory disorders. Familiarize yourself with the bronchial tree, noting that the right lung has one primary bronchus (right principal bronchus) and one primary bronchus (left principal bronchus), which further branch into secondary bronchi, and then tertiary bronchi, ultimately leading to the primary bronchial segments and lobules in both lungs.

This knowledge is essential for interpreting chest X-rays, locating pathologies, and guiding diagnostic and therapeutic interventions in clinical practice.