Atelectasis is caused by which of the following?

Atelectasis refers to the partial or complete collapse of the lung, leading to reduced or absent air exchange in the affected areas. This condition can result from various factors, but the defining characteristic is the collapse of lung tissue. When part or all of the lungs collapses, it compromises the normal expansion and function of the lung, contributing to respiratory distress and reduced oxygenation of the blood.

The correct answer highlights this inherent aspect of atelectasis—specifically, that it involves the collapse of lung tissue. Understanding this helps in recognizing how the physical changes in lung structure directly affect respiratory efficiency and overall health. Recognizing conditions leading to atelectasis, such as obstruction or compression, can be crucial in clinical practice, as prompt intervention is often needed to restore normal lung function.