Question

In mammals, pleural membranes cover the lungs as well as inside of the ribcage. The pleural fluid in between the two membranes:

• A. Dissolves oxygen for transfer to the alveoli
• B. Dissolved CO${}_2$ for transfer to the blood
• C. Provides partial pressure
• D. Reduces the friction between the ribs and the lungs

Answer 1

The correct option is D Reduces the friction between the ribs and the lungs

The lungs are placed inside the abdominal thoracic cavity which is enclosed by the rib cage. The lungs are covered with the pleural membrane which lines the lungs and the rib cage. The pleural fluid which is present between the membranes provides protection to the lungs and prevents friction between the rib cage and the lungs during the process of breathing.

Thus, the correct answer is option D.