Question

The lungs can collapse from A. insufficient surfactant production. B. rupture of the parietal pleura. C. overproduction of surfactant. D. Both (A) and (B)

Short answer

D. Both (A) and (B)

Step-by-step solution

- Understanding Surfactant's Role

Surfactant is a substance produced in the lungs that reduces surface tension, preventing the alveoli from collapsing. Without enough surfactant, the alveoli would collapse due to the high surface tension.

- Analyzing Insufficient Surfactant Production

Insufficient production of surfactant can lead to lung collapse. This is because surfactant keeps the alveoli open, and without it, they may collapse due to the pressure differences. Therefore, option A is a possible cause.

- Considering Rupture of the Parietal Pleura

The pleura is a membrane that encases the lungs. A rupture in the parietal pleura can lead to pneumothorax, where air enters the pleural space and causes the lung to collapse. Thus, option B could also cause lung collapse.

- Evaluating Overproduction of Surfactant

Overproduction of surfactant would not typically cause lung collapse. Instead, it might lead to other issues, such as impairing gas exchange. Therefore, option C is not a likely cause.

- Conclusion

From the analysis, both insufficient surfactant production (A) and rupture of the parietal pleura (B) can cause lung collapse. Hence, the combined answer (D) is correct.

Key concepts

surfactant function in lungs

Surfactant is a crucial substance found in the lungs. It is mainly composed of lipids and proteins. The main role of surfactant is to reduce the surface tension within the alveoli.
The alveoli are tiny air sacs in the lungs where gas exchange occurs.
Without surfactant, the surface tension would be too high, causing the alveoli to collapse. When the alveoli collapse, they cannot participate in gas exchange, making it difficult for oxygen to enter the blood and for carbon dioxide to be expelled from the body.
This is why an adequate amount of surfactant is essential for proper lung function.

pleura rupture and pneumothorax

The pleura is a double-layered membrane that surrounds the lungs. The inner layer is called the visceral pleura, and the outer layer is the parietal pleura.
Between these layers is a small amount of fluid that allows them to slide smoothly against each other during breathing.
A rupture in the parietal pleura can lead to a condition known as pneumothorax. Pneumothorax occurs when air enters the pleural space—the area between the two layers—causing the lung to collapse.
This happens because the pressure difference that normally keeps the lungs inflated is disrupted. Symptoms of pneumothorax can include sudden chest pain and shortness of breath. It often requires medical attention to remove the trapped air to allow the lung to re-expand.

alveoli surface tension

Surface tension is the force that acts on the surface of a liquid. In the lungs, it is found on the inner lining of the alveoli.
This tension causes the alveoli to remain tight and influences how easy or difficult it is for them to expand and contract during breathing. High surface tension would make it harder for alveoli to open, potentially leading to their collapse. Surfactant lowers this surface tension, making it easier for the alveoli to stay open and efficiently exchange gases.
Without surfactant, the alveoli would collapse more readily under the pressure of breathing, especially during exhalation. This collapse would severely limit the lung’s ability to take in oxygen and expel carbon dioxide.