Which of the following is a gas exchange region of the lungs?
A. trachea.
B. terminal bronchiole.
C. respiratory bronchiole.
D. mainstream bronchus.
C
that is the best of all the choices.
The gas exchange region of the lungs is the respiratory bronchiole (option C).
The correct answer is C) respiratory bronchiole.
To get the answer, you can understand the structure and function of the different regions of the lungs.
The trachea (option A) is the tube-like structure that connects the larynx to the bronchi. It is responsible for maintaining an open airway, but it does not participate directly in gas exchange with the blood.
The terminal bronchioles (option B) are the smallest branches of the bronchi in the respiratory system. While they are responsible for conducting air to the respiratory bronchioles, they do not participate in gas exchange either.
The respiratory bronchioles (option C), however, are the first branches of the respiratory zone of the lungs, where actual gas exchange occurs. They contain small air sacs called alveoli, which are surrounded by blood vessels. Oxygen from inhaled air passes through the alveolar walls and into the bloodstream, while carbon dioxide diffuses out of the bloodstream and into the alveoli to be exhaled.
The mainstream bronchus (option D) refers to the primary bronchus, which is the largest bronchus and branches into the lobes of the lungs. Although it plays a key role in conducting air to different parts of the lungs, it is not a gas exchange region.
Therefore, the correct answer is C) respiratory bronchiole.