Chapter 34, Problem 3STP

Summary Introduction

Introduction : 

Lungs are the crucial organ in the body that takes part in the breathing process. They are connected with the nasal cavity with the help of the trachea through which air from the external environment reaches the lungs and the one present in the lungs are expelled out through the same route. In the lungs, oxygen is exchanged for carbon dioxide between the blood capillaries and lung tissues. A diagram representing a different part of a lung is shown below:

Answer to Problem 3STP

Correct answer : 

The correct answer is option (A) 1.

Explanation of Solution

Explanation/justification for the correct answer :

Option (A) 1. Alveoli are the sac-like structure present at the ends of every tertiary bronchus. Alveoli are surrounded by a large number of capillaries and are the site of gaseous exchange between blood and lungs. It is not covered with cilia. So, the correct answer is option (B).

Explanation for incorrect answer : 

Option (B) 2. The bronchus is a tube-like structure that connects the trachea with different structures present in both the lung. The trachea is first divided into primary Bhronchi which are directed into each lung where it is further divided into the secondary and tertiary bronchus. The epithelium of the primary bronchus is covered with cilia which are hair-like structures that trap dirt and large microbes present in the air from entering the lungs. So, this is an incorrect option.

Option (C) 3. The inferior lobe is present behind and below the fissures and forms the base of the lungs. It takes part in expanding the lung area during inhalation. No hairs like structures are present in this region. So, this is an incorrect answer.

Option (D) 4. The middle lobe is present in the right lung and has arterial supply. Arteries carrying deoxygenated blood and oxygenated blood both are present in this region. No hairs like structures are present in this region. So, this is an incorrect answer.