Question

Sequence of branching in bronchial tree is
(A) Segmental bronchi
(B) Lobar bronchi
(C) Terminal bronchioli
(D) Respiratory bronchioli
Choose the correct answer from the options given below:

• A. (A), (B), (C), (D).
• B. (B), (A), (C), (D).
• C. (B), (A), (D), (C).
• D. (A), (B), (D), (C).

Hint:

To remember the sequence easily:
- Conducting zone: Primary Bronchus $\rightarrow$ Lobar Bronchus $\rightarrow$ Segmental Bronchus $\rightarrow$ Bronchioles $\rightarrow$ Terminal Bronchiole.
- Respiratory zone: Respiratory Bronchiole $\rightarrow$ Alveolar Duct $\rightarrow$ Alveolar Sac.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The respiratory system's conducting and respiratory passages form a highly branched structure called the bronchial tree, which distributes inhaled air to the alveoli for gas exchange.

Step 2: Detailed Explanation:
Let us trace the path of air downstream from the trachea into the lungs, establishing the anatomical hierarchy of the bronchial tree from proximal to distal:
1. Trachea: Divides at the carina into right and left principal (primary) bronchi.
2. Lobar Bronchi (B) [Secondary Bronchi]:
Each principal bronchus divides into lobar bronchi, which supply the individual lobes of the lungs.
3. Segmental Bronchi (A) [Tertiary Bronchi]:
Lobar bronchi branch further into segmental bronchi, which supply distinct bronchopulmonary segments within each lobe.
These continue to branch progressively into smaller bronchioles, which lack cartilage in their walls.
4. Terminal Bronchioles (C):
These are the smallest, final conducting bronchioles that do not contain alveoli in their walls and do not participate in gas exchange.
5. Respiratory Bronchioles (D):
The terminal bronchioles divide into respiratory bronchioles, which have thin-walled outpocketings (alveoli) in their walls, marking the beginning of the respiratory (gas exchange) division of the lungs.
Therefore, the correct sequence from proximal (beginning of the tree) to distal (end of the tree) is:
Lobar bronchi (B) $\rightarrow$ Segmental bronchi (A) $\rightarrow$ Terminal bronchioli (C) $\rightarrow$ Respiratory bronchioli (D).

Step 3: Final Answer:
The correct option is (B), representing (B), (A), (C), (D).